Paper.docx · Web viewdetermining the origin of clustering and switching abilities during verbal fluency tasks: a lesion study. abstract

DETERMINING THE ORIGIN OF CLUSTERING

AND SWITCHING ABILITIES DURING VERBAL

FLUENCY TASKS: A LESION STUDY

1

Abstract

The study “Determining the Origin of Clustering and Switching Abilities During Verbal

Fluency Tasks: A Lesion Study” tried to determine which brain regions are critical to verbal

fluency and its associated strategies, clustering words together and switching between clusters.

The study holds importance because understanding where clustering and switching occur in the

brain can serve as a way to preliminarily diagnose where tumors are in a patient’s brain. Eighty-

two subjects were used with a focal lesion in the left frontal, right frontal, left temporal, or right

temporal lobe. Semantic and phonemic scoring criteria for strategies were made for

categorization and letter fluency tasks to score subjects’ verbal fluency tests, which were

collected from the brain tumor database at Froedtert Medical Hospital. Results found that for

the overall words generated, left side damage to the brain resulted in lower scores than right

side damage in categorization tasks, p<0.001, and letter tasks, p=0.001; in letter tasks, frontal

lobe damage resulted in lower scores than temporal damage, p=0.002. All tasks showed that

left side damage would lower scores for the number of clusters produced (α=0.05), and some

significance was found or scores trended to suggest that left side damage would adversely

affect the size of clusters and the number of switches produced. The study provides novel

scoring guidelines for verbal fluency tasks, and the results imply an associative frontal-temporal

network for verbal fluency in the left hemisphere where the frontal lobe is important for

executive functioning and the temporal lobe provides stored information.

2

Thank you to everyone who supported me in this project. Every kind word and constructive

criticism helped me reach my goals.

Thank you to Dr. Sabsevitz for mentoring me in this project. For every question, for all the

resources you made available to me, for all the time you gave me, thank you so very much.

In addition, thank you to everyone else at Froedtert who helped me with finding files and even

with reading handwriting.

Thank you to Mr. Scheuer. For the second year in a row, you have been a caring and intelligent

mentor, able to guide me in the right direction and help me develop my project to its full

potential.

Thank you to Dr. Swanson. As always, I greatly appreciated all your advice and support.

Thank you to Mrs. Trepte for all your interest and support in my project.

Thank you to my parents. Every step of the way, you have done everything you can to make

sure I am able to pursue my love of science, and I cannot express how much your support has

meant.

Thank you to Sara Miller and Seth Johnson—your support was critical to my project and your advice was invaluable.

3

Table of Contents

I. STATEMENT OF THE PROBLEM……………………………………………6

II. DEFINITION OF TERMS…………………………………………………………7

III. LITERATURE REVIEW……………………………………………………………8

IV. RESEARCH QUESTIONS, HYPOTHESIS, AND MATERIALS........39

V. METHOD AND PRODECURE…………………………………………………40

VI. RESULTS………………………………………………………………………………45

VII. CONCLUSION………………………………………………………………………49

VIII. BIBLIOGRAPHY……………………………………………………………………55

4

Lists of Figures

FIGURES

I. PLANES OF THE BRAIN……………………………………………………………8

II. DESCRIBING THE BRAIN DIRECTIONALLY……………………………….8

III. MODEL OF THE BRAIN……………………………………………………………11

IV. BRAIN MRI CONTAINING LESIONS………………………………………....38

V. TOTAL WORD GENERATION DURING

CATEGORIZATION AND LETTER TASKS……………………………………46

VI. AVERAGE NUMBER OF SEMANTIC CLUSTERS

PRODUCED DURING CATEGORIZATION AND LETTER TASKS……48

VII. AVERAGE NUMBER OF PHONEMIC CLUSTERS

PRODUCED DURING CATEGORIZATION AND LETTER TASKS …..48

5

Statement of the Problem

One of the greatest neurological questions is a basic one: what are the functions of

different brain regions? This study seeks to determine the regions important to verbal fluency,

and which brain regions function to facilitate strategies for clustering words and switching

between clusters. Researching these strategies allows for a greater understanding of how

words and language are organized in the brain.

Establishing the location of clustering and switching abilities can also assist in tumor

detection. If a verbal fluency test is given to a patient and the scores for clustering and

switching are very low, a neurologist may have a better idea of where the origin of a patient’s

problem stems from. Knowing where the brain deficits may be originating can make the

diagnosis and treatment process for a patient smoother and more efficient. Therefore, studies

like the current one are needed to take the first step towards establishing the functions of brain

regions in order for better diagnoses.

6

Definition of Terms

1. Categorization Testing—A verbal fluency test where a subject must produce words relating to a specific semantic category (ex. animals).

2. Clustering—The grouping of words based on a common semantic or phonemic category. Clustering is a good measure of person’s ability to organize and retrieve relevant information.

3. Letter Testing—A verbal fluency test where a subject must produce words starting with a specific letter. The test is usually given as a set of three separate letter tests, usually consisting of F,A,S or C,F,L for letters.

4. Phonemic Scoring—Scoring of verbal fluency tests based on finding clusters with words that relate by how they sound or how they are spelled.

5. Semantic Scoring—Scoring of verbal fluency tests based on finding clusters with words that relate categorically or by definition.

6. Switching—The act of moving from one cluster directly into the next. Switching is seen as a mentally effortful task and can be viewed a measure of one’s executive thinking.

7. Verbal Fluency Testing—Neuropsychological tests created to measure the quantity of words a subject can produce within a certain time, usually a minute. Tests are also usually restricted to certain semantic or phonemic categories, such as giving a letter or categorization test.

7

Literature Review

Introduction

This study examines the effect lesion location has on clustering and switching abilities

during verbal fluency tasks. Considerable research was done to understand the topic before

research began. The brain needed to be studied extensively, especially the cerebrum, in order

to understand both the anatomies and functions of the areas that would be worked with in the

study. Verbal fluency tests, the “tool” being used to measure clustering and switching abilities,

needed to be studied as well, and research was collected on both semantic and phonemic

fluency. Information about verbal fluency tests that looked at clustering and switching were

given special attention, and general factors that could affect the outcomes of verbal fluency

tests were considered as well. Finally, brief overviews on lesions and lesion studies were

provided to explain the technology in the study and type of study being conducted.

The Brain

Key Information for Discussing the Brain

The three orthogonal planes, or “main views,” used for looking at the brain are axial,

coronal, and sagittal planes1. The axial view, also called a horizontal view, is a slice of the brain

parallel to the floor (if the subject is standing up). The coronal view is a vertical slice, parallel to

the face. And a sagittal slice is a vertical slice as well, perpendicular to the face2.

Figure 13

1 Becker, Alex J. and Johnson, Keith A. “The Whole Brain Atlas.” Harvard University. Web. 21 Jul. 2012., Castillo, Joseph. “Fundamentals of Image Interpretation.” Web. 21 Jul. 2012.

2 Blumenfeld, Hal. Neuroanatomy Through Clinical Cases. Sunderland: Sinauer Associates Inc., 2002. Print.

8

Certain terms clarify the location of parts of the brain. The term “superior” refers to

towards the top, while “inferior” refers to towards the bottom4. “Anterior” refers to the front of

a structure, while “posterior” refers to towards the rear of a structure5. Above the midbrain,

superior means dorsal, inferior means ventral, anterior means rostral, and posterior means

caudal. But, because of the midbrain-diencephalic junction, the brain has a ninety degree shift

in direction, causing naming to change. Under the midbrain, superior means rostral, inferior

means caudal, anterior means ventral, and posterior means dorsal6.

Figure 2

General Overview of the Brain

The general nervous system has two parts: the central nervous system (CNS) and the

peripheral nervous system (PNS). The central nervous system contains the spinal cord and brain

and the peripheral nervous system is made up of nerves7. The CNS forms originally from the

neuronal tube, and this tube’s cavities eventually become ventricles, which fill up with

cerebrospinal fluid8. Two notable ventricles, one in each hemisphere of the brain, form as C-

shapes9. In addition, both the brain and spinal cord contain gray and white matter10. This gray

matter contains the most neurons, while white matter is composed of axons and colored white 3 Das, Rajesh et al. Orthographic Viewer. Eplasty. Objective Three-Dimensional Analysis of Cranial

Morphology. Edited Image. 13 Aug. 2012. 4 Blumenfeld, Hal. Neuroanatomy Through Clinical Cases. Sunderland: Sinauer Associates Inc., 2002.

Print.5 Blumenfeld, Hal. Neuroanatomy Through Clinical Cases. Sunderland: Sinauer Associates Inc., 2002.

Print., “Posterior.” The Free Dictionary, 2012. Farlax. Web. 8 Aug. 2012.6 Blumenfeld, Hal. Neuroanatomy Through Clinical Cases. Sunderland: Sinauer Associates Inc., 2002.

Print.7 Blumenfeld, Hal. Neuroanatomy Through Clinical Cases. Sunderland: Sinauer Associates Inc., 2002.

Print., “Brain Structures and Their Functions.” Serendip, 1994. Bryn Maur College. Web. 25 Jul. 2012., “Nervous Tissue.” Rutgers University. 2012. Web. 12 Jul. 2012.


9 Snell, Richard S. Clinical Neuroanatomy for Medical Students. Philadelphia: Lippincott-Raven Publishers, 1997. Print.

10 “Nervous Tissue.” Rutgers University. 2012. Web. 12 Jul. 2012.

9

by the axons’ myelin sheathes; in the brain, the inner core is made up of white matter, while

the outside of the brain contains gray matter11.

The cells of the nervous system are neurons. They have a cell body, as well as axons and

dendrites. These axons and dendrites help with communication throughout the body—

dendrites receive output and axons carry/pass on output— and help with the formation of

synapses12. The brain contains over ten billion neurons13.

Other notable cells in the brain include glial cells and meninges. Glial cells, referred to as

support cells, connect tissue within the central nervous system14. They hold CNS neurons in

place and keep axons insulated to prevent “short circuits15.” The cells can be classified as

microglia, oligodendrocytes, and astrocytes16. In addition, meninges are coverings of the brain.

The three layers of meninges consist of dura mater, arachnoid, and pia mater17. Another

protector of the brain is the cerebral spinal fluid18.

The brain is made up of three main parts: the forebrain (prosencephalon), the midbrain

(mesencephalon), and the hindbrain (rhombencephalon); the midbrain connects the forebrain

to the hindbrain. The forebrain can be broken up into the telencephalon, containing the

cerebral hemispheres, and the diencephalon, the central part of the forebrain which contains

the thalamus, hypothalamus, and epithalamus. The brain also has a left and right hemisphere—

these hemispheres are separated at a midline called the interhemispheric, or longitudinal,

tissue. The two hemispheres are connected by the corpus callosum, made up of white matter19.

11 “Gray Matter vs. White Matter.” Neuroscience Intelligence: Behavioral Neuroscience Web Ring [at] Macalester College. Web. 14 Jul 2012., Overney, Gregor T. “Exploration of Human Brain Tissue.” Microscopy UK, 2002. Web. 12 Jul. 2012., Snell, Richard S. Clinical Neuroanatomy for Medical Students. Philadelphia: Lippincott-Raven Publishers, 1997. Print.

12 Blumenfeld, Hal. Neuroanatomy Through Clinical Cases. Sunderland: Sinauer Associates Inc., 2002. Print., “Nervous Tissue.” Rutgers University. 2012. Web. 12 Jul. 2012.

13 Overney, Gregor T. “Exploration of Human Brain Tissue.” Microscopy UK, 2002. Web. 12 Jul. 2012.14 Blumenfeld, Hal. Neuroanatomy Through Clinical Cases. Sunderland: Sinauer Associates Inc., 2002.

Print., “Nervous Tissue.” Rutgers University. 2012. Web. 12 Jul. 2012., Overney, Gregor T. “Exploration of Human Brain Tissue.” Microscopy UK, 2002. Web. 12 Jul. 2012.

15 Overney, Gregor T. “Exploration of Human Brain Tissue.” Microscopy UK, 2002. Web. 12 Jul. 2012.16 “Nervous Tissue.” Rutgers University. 2012. Web. 12 Jul. 2012. 17 Blumenfeld, Hal. Neuroanatomy Through Clinical Cases. Sunderland: Sinauer Associates Inc., 2002.

Print., “Nervous Tissue.” Rutgers University. 2012. Web. 12 Jul. 2012.18 “CSF.” Dictionary.com, 2012. Web. 12 Jul. 2012., Snell, Richard S. Clinical Neuroanatomy for Medical

Students. Philadelphia: Lippincott-Raven Publishers, 1997. Print.19 Blumenfeld, Hal. Neuroanatomy Through Clinical Cases. Sunderland: Sinauer Associates Inc., 2002.

Print., Snell, Richard S. Clinical Neuroanatomy for Medical Students. Philadelphia: Lippincott-Raven Publishers, 1997. Print.

10

Different parts of the brain have separate functions. The cerebrum is generally used to

formulate thoughts and actions and includes the cerebral cortex20. The cerebrum’s cerebral

cortex is the “last receiving station…it relates the received information to past memories21.” The

cortex has four main lobes: the frontal lobe, temporal lobe, parietal lobe, and occipital lobe.

The frontal lobe (generally) is used for reasoning, planning, speech, movement, emotions, and

problem solving. The temporal lobe is used for perception, auditory stimuli, memory, and

speech. The parietal lobe is used for movement, orientation, recognition, and perceiving

stimuli. The occipital lobe is used for visual processing. Outside of the cerebrum is the

cerebellum, an area of the brain associated with coordination, posture, and balance22. The

cerebellum also has associations with learning, planning, judging time, emotional control,

attention, and perception23. The brain contains its oldest part, the brain stem, which is up of the

midbrain, pons, and medulla24. The brain stem controls automatic, basic life functions such as

heartbeat and breathing25.

Figure 326

Anatomy of the Cerebrum and Cerebral Cortex

20 “Brain Structures and Their Functions.” Serendip, 1994. Bryn Maur College. Web. 25 Jul. 2012.21 Snell, Richard S. Clinical Neuroanatomy for Medical Students. Philadelphia: Lippincott-Raven Publishers,

1997. Print.22 “Brain Structures and Their Functions.” Serendip, 1994. Bryn Maur College. Web. 25 Jul. 2012.23 Leggio, Maria Giuseppa et al. “Phonological Grouping is Specifically Affected in Cerebellar Patients: A

Verbal Fluency Study.” J. Neurol. Neurosurg. Psychiatry, 2000; 69:102-106. BMS Publishing Group. Web. 31 Jul. 2012.

24 Blumenfeld, Hal. Neuroanatomy Through Clinical Cases. Sunderland: Sinauer Associates Inc., 2002. Print., “Brain Structures and Their Functions.” Serendip, 1994. Bryn Maur College. Web. 25 Jul. 2012.

25 “Brain Structures and Their Functions.” Serendip, 1994. Bryn Maur College. Web. 25 Jul. 2012.26 Untitled. 1995. Intelegen Inc. Overview of the Brain. Image. 13 Aug. 2012.

11

The gray matter on the surface layer of the cerebrum’s hemispheres is known as the

cerebral cortex27.The cerebrum’s cerebral cortex contains six layers of cell bodies: the

superficial molecular layer, outer granular layer, pyramidal cell layer, inner granular layer,

internal pyramid layer, and polymorphic cell layer.28 Numerous crevices on the cerebral cortex

are known as sulci, and the bumps or ridges between the sulci are called gyri29. When sulci are

large enough, they are able to separate the cerebrum into lobes, which is why the frontal,

temporal, parietal, and occipital lobes exist.

The brain also contains association fibers. These fibers usually connect regions in the

same hemisphere, but can also connect regions across different hemispheres. For instance, the

uncinate faciculus “connects [the] first motor speech area and the gyri on the inferior surface of

the frontal lobe with the cortex of the pole of the temporal lobe.” Other association fibers

connect the frontal lobes to the temporal lobes as well, including the cingulum, superior

longitudinal fasciculus, and fronto-occipital fasciculus30.

The frontal lobe is predictably in the front of the brain, anterior to the central sulcus (of

Rolando)31. The frontal lobe is separated from the parietal lobe by the central sulcus32. The

frontal lobe is lateral to and separated from the temporal lobe by the Sylvian fissure, also called

the lateral fissure; a parieto-occipital sulcus helps to separate the frontal and temporal lobes as

well33. Within the front lobe, notable gyri include the precentral gyrus, the superior frontal

gyrus, the middle frontal gyrus, and the inferior frontal gyrus. The precentral gyrus contains 27 Snell, Richard S. Clinical Neuroanatomy for Medical Students. Philadelphia: Lippincott-Raven Publishers,

1997. Print.28 “Nervous Tissue.” Rutgers University. 2012. Web. 12 Jul. 2012., Baciu, Monica et al. “Hemispheric

Predominance Assessment of Phonology and Semantics: A Divided Visual Field Experiment.” Brain and Cognition, 2006; 61: 298-304. Elsevier. Web. 30 Jul. 2012., Badewien, Meike. “Differential Prefrontal and Frontotemporal Oxygenation Patterns During Phonemic and Semantic Verbal Fluency.” Neuropsychologia, June 2012; 50(7): 1565-1569. Elsevier and ScienceDirect. Web. 31 Jul. 2012.

29 Blumenfeld, Hal. Neuroanatomy Through Clinical Cases. Sunderland: Sinauer Associates Inc., 2002. Print., Snell, Richard S. Clinical Neuroanatomy for Medical Students. Philadelphia: Lippincott-Raven Publishers, 1997. Print.





12

posterior parts of the superior, middle, and inferior frontal gyri, and while the posterior region

is a motor area monitoring individual movements, the anterior area is more of a premotor area

used for storing information on how to move34. The inferior frontal lobe can be split into four

main regions: the pars triangularis, pars orbitalis, dorsal pars opercularis, and ventral pars

opercularis35. Within the inferior frontal region, Broca’s area is also contained—this area is

associated with speech functions because it connects to primary motor areas and helps with

the formation of words36.

The other lobes of the brain, in different locations than the frontal lobe, are split up into

smaller sections as well. The temporal lobe is an area inferior to the lateral sulcus. Superior and

medial temporal sulci split the lobe into superior, middle, and inferior temporal gyri. The

temporal gyrus also contains areas such as the primary auditory area (including the gyrus of

Heschl), the secondary auditory area, and the sensory speech area of Wernicke. Next, the

parietal lobe is posterior to the central sulcus and superior to the lateral sulcus, and extends

back to the pareito-occipital sulcus. Notable parts of the parietal lobe include the superior

parietal gyrus and the inferior parietal gyrus. The final lobe, the occipital lobe, is a small area

contained posterior to the pareito-occipital sulcus37.

Movement for one side of the body takes place in the primary motor cortex, found in

the precentral/anterior gyrus of the frontal lobe; the other side of the body’s movement is

controlled by the primary somatosensory cortex in the postcentral/posterior gyrus of the

parietal lobe.


35 “Pars Orbitalis.” Dictionary.com, 2012. Web. 29 Jul. 2012., Price, Cathy J. “The Anatomy of Language: A Review of 100 fMRI Studies Published in 2009.” Annals of the New York Academy of Sciences, 2912; 1191: 62-88. Print.

36 Price, Cathy J. “The Anatomy of Language: A Review of 100 fMRI Studies Published in 2009.” Annals of the New York Academy of Sciences, 2912; 1191: 62-88. Print., Snell, Richard S. Clinical Neuroanatomy for Medical Students. Philadelphia: Lippincott-Raven Publishers, 1997. Print.


13

A higher level of sensory and motor interpretation is also found in the association

cortex38. This cortex contains parts of the prefrontal, anterior temporal, and posterior parietal

cortexes39.

Verbal Fluency Testing

Verbal Fluency Tests

Verbal fluency tests, or tests of “Controlled Oral Word Association,” are

neuropsychological tests designed to measure the timed, oral production of words when word

generation is restricted40. Measurement is done quantitatively—the number of words produced

is recorded41. For both semantic and phonemic verbal fluency tests, subjects need access to

lexical memory, or access to memory of various words42. With this access to lexical memory,

subjects must be able to initiate word generation, effectively search for words, and retrieve the

information for executive/articulation43. To do well on verbal fluency tests, a subject also needs

a semantic store for his or her knowledge of words and an effective search strategy to gather

information quickly. Subjects do poorly when they lack either a knowledge base or efficient

search process44.

The two common types of verbal fluency tests are semantic (category) and phonemic

(letter) fluency tasks (described in detail below). Although both types are measures of verbal

fluency and overlap in where they take place in the brain, semantics and phonemics are said to

function individually of each other in the brain45. Typically, examiners should expect subjects to 38 Blumenfeld, Hal. Neuroanatomy Through Clinical Cases. Sunderland: Sinauer Associates Inc., 2002.

Print., Snell, Richard S. Clinical Neuroanatomy for Medical Students. Philadelphia: Lippincott-Raven Publishers, 1997. Print.


40 Barker, R.A. et al. “Verbal Fluency in Huntington’s Disease: A Longitudinal Analysis of Phonemic and Semantic Clustering and Switching.” Neuropsychologia, 2002; 40(8): 1277-84. Elsevier. Web. 31 Jul. 2012., Sherman, Elisabeth MS et al. A Compendium of Neuropsychological Tests. New York: Oxford University Press, 2006. Print.

41 Grabowska, Anna et al. “Phonological and Semantic Fluencies are Mediated by Different Regions of the Prefrontal Cortex.” Acta. Neurobiol. Exp., 2000; 60: 503-508. Web. 30 Jul. 2012.

42 Grabowska, Anna et al. “Phonological and Semantic Fluencies are Mediated by Different Regions of the Prefrontal Cortex.” Acta. Neurobiol. Exp., 2000; 60: 503-508. Web. 30 Jul. 2012., “Lexical.” Dictionary.com, 2012. Web. 29 Jul. 2012.

43 John, Sunila et al. “Qualitative Analysis of Clustering on Verbal Fluency in Young Adults.” Language in India, Jul. 2011; 11. Web. 31 Jul. 2012.

44 Sherman, Elisabeth MS et al. A Compendium of Neuropsychological Tests. New York: Oxford University Press, 2006. Print.

45 Beaucousin, V. et al. “Meta-analyzing Left Hemisphere Language Area: Phonology, Semantics, and Sentence Processing.” Neuroimage, May 2006; 30(4): 1414-32. PubMed. Web. 30 Jul. 2012., Horemans, I.

14

do better on category, or semantic, tasks than letter, or phonemic, tasks; whether or not this is

because semantic information for speech production is available in the brain before phonemic

information has not been proven46. In any case, verbal fluency tasks are imperative clinically for

finding cognitive deficits in patients, although “deficits on tests of verbal fluency do not by

themselves provide evidence of executive dysfunction47.” They are, however, an important step

in realizing a patient may need treatment.

Information Specific to Semantics and Semantic Testing

Auditory speech processing is the process of “extracts[ing] meaningful information from

continuously changing acoustic inputs.” When these inputs are successfully transferred into

meaningful messages, it is known as semantics48. Semantics pertains to the different meanings

of word and symbols and the ability to interpret and analyze these meanings49. The semantic

process during speech production is said to come after a subject conceives of what is being

heard but before phonological encoding; however, for auditory speech comprehension,

phonological information is available before semantic information50. Speech/semantic

comprehension must come from prior knowledge and what people expect to be said; each

semantic fluency task requires a subject’s search of conceptual knowledge before grouping

answers according to semantic categories51. In this way, language comprehension is a product

of top-down processing, or the process of using previous knowledge to influence interpretation

et al. “The Influence of Semantic and Phonological Factors on Syntactic Decisions: An Event-Related Brain Potential Study.” Psychophysiology, Nov 2003; 40(6): 869-77. PubMed. Web. 30 Jul. 2012.,

46 Baldo, Juliana et al. “Pervasive Influence of Semantics in Letter and Category Fleuncy: A Multidimensional Approach.” Brain and Language, 2003, Academic Press. Web. 31 Jul. 2012., Horemans, I. et al. “The Influence of Semantic and Phonological Factors on Syntactic Decisions: An Event-Related Brain Potential Study.” Psychophysiology, Nov 2003; 40(6): 869-77. PubMed. Web. 30 Jul. 2012., John, Sunila et al. “Qualitative Analysis of Clustering on Verbal Fluency in Young Adults.” Language in India, Jul. 2011; 11. Web. 31 Jul. 2012., Sherman, Elisabeth MS et al. A Compendium of Neuropsychological Tests. New York: Oxford University Press, 2006. Print.


48 Price, Cathy J. “The Anatomy of Language: A Review of 100 fMRI Studies Published in 2009.” Annals of the New York Academy of Sciences, 2912; 1191: 62-88. Print.

49 “Semantics.” Dictionary.com, 2012. Web. 29 Jul. 2012.50 Horemans, I. et al. “The Influence of Semantic and Phonological Factors on Syntactic Decisions: An

Event-Related Brain Potential Study.” Psychophysiology, Nov 2003; 40(6): 869-77. PubMed. Web. 30 Jul. 2012.

51 Grabowska, Anna et al. “Phonological and Semantic Fluencies are Mediated by Different Regions of the Prefrontal Cortex.” Acta. Neurobiol. Exp., 2000; 60: 503-508. Web. 30 Jul. 2012., Price, Cathy J. “The Anatomy of Language: A Review of 100 fMRI Studies Published in 2009.” Annals of the New York Academy of Sciences, 2912; 1191: 62-88. Print.

15

and classification of new stimuli52. Studies have even pointed out that semantic responses are

at first automated and then come from personal memories; for instance, if naming animals for

a semantic fluency test, personal answers may include pets the subjects has owned53. At the

same time, activation seen in the medial superior frontal cortex “may reflect the demands on

executive strategies that are necessary for, but not limited to, semantic word retrieval54.”

Overall, semantic fluency has been described as both automated (because responses are

already in previous knowledge) and also as using some executive functions55.

For semantic fluency tests, naming animals is the commonest category; food is another

common one. Subjects usually do better on semantic tests than phonemic ones because

semantics have ‘naturally’ occurring subcategories; without directions, people are likely to, for

example, name animals by the places they originate from. Tests of semantic fluency are

important for predicting actual communication skills; that is, they are measuring a person’s

ability to retrieve and express thoughts56.

Information Specific to Phonemics and Phonemic (Letter) Testing

Phonemic testing is focused on phonemes, small sets of speech sound units that create

words and sentences. A common phoneme would be a letter57. During phonemic testing, an

“examinee must produce orally as many words as possible beginning with a specified letter

during a fixed period of time, usually a minute.” In other words, the examinee, or subject, is

given a letter of the alphabet and must generate words beginning with that letter. The most

commonly used letters in a set for the test are F, A, and S, although other sets have been used

somewhat regularly as well (C, F, L and P, R, W). Letter consideration is important, however,

52 Price, Cathy J. “The Anatomy of Language: A Review of 100 fMRI Studies Published in 2009.” Annals of the New York Academy of Sciences, 2912; 1191: 62-88. Print., “Top-down Processing.” Dictionary.com, 2012. Web. 29 Jul. 2012.

53 Moscovitch, Morris and Sheldon, Signy. “The Nature and Time-Course of Medial Temporal Lobe Contributions to Semantic Retrieval: An fMRI Study on Verbal Fluency.” Hippocampus, June 2012; 22(6): 1451-1466. Wiley Periodicals. Web. 31 Jul. 2012.




57 “Phoneme.” Dictionary.com, 2012. Web. 29 Jul. 2012.

16

because the difficulty to produce words starting with a certain letter can affect test outcomes58.

Using Q, for example, would make a phonemics test significantly harder than using A.

Phonemic tests, are a good measure of a subject’s ability to “suppress the ordinary way

of retrieving words from memory according to their meaning59.” In other words, phonemic tests

show subjects’ abilities to choose from competing verbal responses while organizing their

thoughts and finding words with a ‘nonhabitual strategy,’ (a nonhabitual strategy refers to a

novel way of gathering information, and people usually do not search for information

phonologically)60. Because these tests force subjects to take extra time to internally “test lexical

candidates beginning with a certain sound,” studies have hypothesized that phonemic fluency

takes more articulatory planning than semantic fluency61. In fact, phonemic fluency is seen as

an almost completely executive functioning process62. Studies that disagree with this theory

may admit the executive role needed for phonemic fluency, but also believe that semantic

strategies are still regularly applied to word retrieval63.

Clustering and Switching

According to Troyer et al (1997), optimal fluency scores are accompanied by proficient

clustering and switching techniques64. Clustering refers to generating words successively in a

subcategory and has also been described as a “spreading activation model in which words are

represented as interconnected nodes that altogether form structured semantic networks65.” In


59 Grabowska, Anna et al. “Phonological and Semantic Fluencies are Mediated by Different Regions of the Prefrontal Cortex.” Acta. Neurobiol. Exp., 2000; 60: 503-508. Web. 30 Jul. 2012.

60 Ali, Nilufa et al. “Structural Correlates of Semantic and Phonemic Fluency Ability in First and Second Languages.” Cereb. Cortex, Nov. 2009; 19(11): 2690-2698. NCBI. Web. 30 Jul. 2012., Barker, R.A. et al. “Verbal Fluency in Huntington’s Disease: A Longitudinal Analysis of Phonemic and Semantic Clustering and Switching.” Neuropsychologia, 2002; 40(8): 1277-84. Elsevier. Web. 31 Jul. 2012., Sherman, Elisabeth MS et al. A Compendium of Neuropsychological Tests. New York: Oxford University Press, 2006. Print.

61 Ali, Nilufa et al. “Structural Correlates of Semantic and Phonemic Fluency Ability in First and Second Languages.” Cereb. Cortex, Nov. 2009; 19(11): 2690-2698. NCBI. Web. 30 Jul. 2012.


63 Baldo, Juliana et al. “Pervasive Influence of Semantics in Letter and Category Fleuncy: A Multidimensional Approach.” Brain and Language, 2003, Academic Press. Web. 31 Jul. 2012.


65 Baldo, Juliana et al. “Pervasive Influence of Semantics in Letter and Category Fleuncy: A Multidimensional Approach.” Brain and Language, 2003, Academic Press. Web. 31 Jul. 2012., Barker, R.A. et al. “Verbal Fluency in Huntington’s Disease: A Longitudinal Analysis of Phonemic and Semantic Clustering and Switching.” Neuropsychologia, 2002; 40(8): 1277-84. Elsevier. Web. 31 Jul. 2012.,

17

other words, clustering, which has also been called ‘sequential priming effect,’ acknowledges

that words said previously affect following answers’ semantic or phonemic characteristics66. To

better understand the idea of clustering, one could compare it to word classification, or the

study of how “environment is broken down into classes of entities67.”

Switching refers to switching or transitioning into new subcategories68. Switching is

judged as a measure of cognitive flexibility and is viewed as a relatively effortful task69. Keeping

track of scores like switching and clustering are important to learning about organizational and

executive strategies; when these strategies are absent in subjects, executive disorders are more

easily able to be found70.

During semantic fluency tests, clustering semantically means sticking within a semantic

subcategory (for example, naming jungle animals when naming animals), and switching

semantically would refer to switching within these categories71. More than one way of grouping

subcategories may occur; for example, when the category is ‘animals,’ subcategories may be

based on where animal is from (ex.African animals), what kind of animal it is considered (ex. pet

animal), or what zoological category the animal is from (ex. birds)72.

When looking at animals, categorizing zoologically depends on external knowledge on

how animals are already grouped. Animals scientifically have a two part name, consisting of

their genus, or species, and then their species within that genus. This genus is considered

Sherman, Elisabeth MS et al. A Compendium of Neuropsychological Tests. New York: Oxford University Press, 2006. Print.


67 Diesendruck, Gil. “Categories for Names or Names for Categories? The Interplay Between Domain-Specific Conceptual Structure and Language.” Language and Cognitive Processes, 2003; 18(5/6): 759-787. Bar-Ilan University. Web. 28 Aug. 2012.





72 John, Sunila et al. “Qualitative Analysis of Clustering on Verbal Fluency in Young Adults.” Language in India, Jul. 2011; 11. Web. 31 Jul. 2012., Troyer, A.K. “Normative Data for Clustering and Switching on Verbal Fluency Tasks.” Journal of Clinical and Experimental Neuropsychology, 2010; 22(3): 370-378. Web. 14 Jan 2013.

18

relatively specific however—every animal genus belongs to a family, within an order, within a

class, within a phylum, within a kingdom of organisms. Within all those levels, the phylum

Chordata contains bilaterally symmetrical organisms, including classes like Amphibia and Avia.

Animals in the class Mammalia are commonly defined by having hair and producing milk73.

Another example would be when the category is furniture: groups would include what

the furniture’s function is, what room the furniture is used in, and what material the furniture is

made out of (ex. wicker)74. Animals and furniture are a good pairing to analyze during semantic

fluency tests because some studies show different mechanisms for processing and

understanding animate and inanimate objects exist even since a person’s infancy. A literature

review done by Diesendruck 2003 points out that animal naming and grouping is less based on

cultural influence than ‘artifact’ naming, and also that inanimate object/artifact naming and

grouping may be more reliant on “labeling” of objects (while animal grouping can be based on

physical/zoological characteristics) because labeling helps give “cohesiveness and psychological

meaning’ to objects75.

During semantic fluency tests, clustering phonemically means sticking within a

phonemic category (for example, naming animals that all start with the letter ‘s’), and switching

phonemically again refers to switching between these groups76. On phonemic fluency tests,

(phonemic) clusters are counted as words generated that contain the first two same letters,

rhyme, are words that differ only by (vowel) sound (ex. fun, fit), end in the same sound, or are

homonyms/most homophones. Switches are switches between these subcategories77. Much of

73 Campbell and Reece. AP Edition Biology. San Francisco: Pearson Education, Inc., 2005. Print.74 “Furniture Categories.” McKay’s Furniture. Web. 28 Aug. 2012. 75 Diesendruck, Gil. “Categories for Names or Names for Categories? The Interplay Between Domain-

Specific Conceptual Structure and Language.” Language and Cognitive Processes, 2003; 18(5/6): 759-787. Bar-Ilan University. Web. 28 Aug. 2012.


77 Barker, R.A. et al. “Verbal Fluency in Huntington’s Disease: A Longitudinal Analysis of Phonemic and Semantic Clustering and Switching.” Neuropsychologia, 2002; 40(8): 1277-84. Elsevier. Web. 31 Jul. 2012., Leggio, Maria Giuseppa et al. “Phonological Grouping is Specifically Affected in Cerebellar Patients: A Verbal Fluency Study.” J. Neurol. Neurosurg. Psychiatry, 2000; 69:102-106. BMS Publishing Group. Web. 31 Jul. 2012., Sherman, Elisabeth MS et al. A Compendium of Neuropsychological Tests. New York: Oxford University Press, 2006. Print., Troyer, A.K. “Normative Data for Clustering and Switching on Verbal Fluency Tasks.” Journal of Clinical and Experimental Neuropsychology, 2010; 22(3): 370-378. Web. 14 Jan 2013.

19

the criteria for a phonemic cluster on a phonemic fluency test may be applied to a semantic

fluency test as well.

Studies have found that during tests of semantic fluency, semantic searches are

common, and both clustering and switching are frequently used search strategies. Subjects

completing tests of phonemic fluency use various phonemic search strategies, such as changing

the stems of words, creating many switches during testing; meanwhile, for phonemic fluency

tasks, clustering is sometimes reported to be less important than to semantic testing78. So

although semantic clustering can be seen in phonemic tasks, and phonemic clustering can occur

during a semantic task, phonemic clusters (if appearing significantly) tend to be analyzed during

tests of phonemic fluency, and semantic clusters are analyzed during tests of semantic

fluency79. For both kinds of verbal fluency tasks, clusters become apparent when one word said

activates an entire ‘network’ of associative words that are related80.

Scoring Tests

Scoring across different studies can be variable; one systematic way of evaluating verbal

fluency tasks does not seem established. At the same time, similar scoring patterns do occur.

Typical scoring includes keeping track of the total words produced, errors, how many words are

produced in a certain amount of time, and the strategies subjects use81.

The total sum score for semantic fluency is the sum of all admissible words in the given

category (across all trials if there is more than one)82. Another way to find semantic (or

phonemic) fluency scores is to find the average number of words a subject generates for each

78 Barker, R.A. et al. “Verbal Fluency in Huntington’s Disease: A Longitudinal Analysis of Phonemic and Semantic Clustering and Switching.” Neuropsychologia, 2002; 40(8): 1277-84. Elsevier. Web. 31 Jul. 2012., Baudu, C. et al. “Clustering and Switching Strategies in Verbal Fluency Tasks: Comparison Between Schizophrenics and Healthy Adults.” J. Int. Neuropsycho. Soc., 1998; 4(6): 539-46. PubMed. Web. 31 Jul. 2012., Troyer, AK. “Clustering and Switching as Two Components of Verbal Fluency: Evidence from Younger and Older Healthy Adults.” Neuropsychology, 1997; 11: 138-146. Baycrest. Web. 31 Jul. 2012.



81 Alexander, Michael P. et al. “Lateralized Cerebellar Contributions to Word Generation: A Phonemic and Semantic Fluency Study.” Behavioural Neurology, 2012; 23(1-2): 31-37. IDS Press. Web. 30 Jul. 2012.

82 Leggio, Maria Giuseppa et al. “Phonological Grouping is Specifically Affected in Cerebellar Patients: A Verbal Fluency Study.” J. Neurol. Neurosurg. Psychiatry, 2000; 69:102-106. BMS Publishing Group. Web. 31 Jul. 2012., Sherman, Elisabeth MS et al. A Compendium of Neuropsychological Tests. New York: Oxford University Press, 2006. Print.

20

category83. Certain rules also apply for which words can be accepted as ‘correct’ on semantic

fluency tests. For instance, if animals was the category, a subject would be allowed to name

extinct, imaginary, or magic animals, but proper names, nonexistent animals (completely made

up during testing), variations of previously said animals (synonyms), any verbs, and repetitions

would not be counted as correct84.

The total sum score for phonemic fluency is usually found by adding all the correct

words from all three trials (one trial per letter)85. Slang or foreign words, as long as they exist,

should be counted as correct, but proper names, nonexistent words, variations of previous said

words, any verbs, and word repetitions are all counted as incorrect answers86. Words in another

language than the one the test is given in are not counted either.

During both semantic and phonemic tests, the examiner is able to prompt a subject to

continue generating words by repeating the instructions if a subject stays quiet for over fifteen

seconds. At the end of the trial for a specific letter or category, the examiner should give extra

time if instructions were repeated. At the end of the trial, the examiner can also ask the subject

any questions. For example, if a subject says “son” and “sun” during a phonemics test for the

letter ‘s,’ an examiner may confirm that the repetition was actually a homophone. The

examiner should also write down all the words produced in the order they were said. Having

the words written down allows for data for additional analysis to be available because even the

order of words can show subjects’ thinking processes87. Errors (for instance, repetitions) are

important to record too as they can give clues to a subject’s disorder88. Continually reverting to 83 Grabowska, Anna et al. “Phonological and Semantic Fluencies are Mediated by Different Regions of the

Prefrontal Cortex.” Acta. Neurobiol. Exp., 2000; 60: 503-508. Web. 30 Jul. 2012.84 John, Sunila et al. “Qualitative Analysis of Clustering on Verbal Fluency in Young Adults.” Language in

India, Jul. 2011; 11. Web. 31 Jul. 2012., Sherman, Elisabeth MS et al. A Compendium of Neuropsychological Tests. New York: Oxford University Press, 2006. Print.

85 Leggio, Maria Giuseppa et al. “Phonological Grouping is Specifically Affected in Cerebellar Patients: A Verbal Fluency Study.” J. Neurol. Neurosurg. Psychiatry, 2000; 69:102-106. BMS Publishing Group. Web. 31 Jul. 2012., Sherman, Elisabeth MS et al. A Compendium of Neuropsychological Tests. New York: Oxford University Press, 2006. Print.

86 John, Sunila et al. “Qualitative Analysis of Clustering on Verbal Fluency in Young Adults.” Language in India, Jul. 2011; 11. Web. 31 Jul. 2012., Sherman, Elisabeth MS et al. A Compendium of Neuropsychological Tests. New York: Oxford University Press, 2006. Print.



21

a specific subcategory, repeating one response, or making intrusions (words in the wrong

category/for the wrong letter) all can be recorded to help diagnose mental deficits89. Three or

more of these types of errors (ex. repetitions) are considered unusual90. And additional testing

over time always provides valuable qualitative data, showing examiners change in their

subjects’ performances and deficits91.

Rules apply for scoring clustering and switching as well. Clusters, for example, must have

at least two words in it to count as a cluster, although a switch can be counted in some studies

even if it’s between “one-word clusters92.” Many studies have only counted phonemic clusters

on phonemic fluency tests, and semantic clusters on semantic fluency tests for measures of

verbal fluency93. In addition, whenever phonemic clusters are being counted, the choice is up to

the examiner whether or not only to count groups of words starting with the same letter as

phonemic clusters, or to count all groups of words that sound the same way as phonemic

clusters94.

There are different ways to calculate cluster and switching scores. One way to measure

cluster size is by the mean cluster size, which is found by summing up the size of clusters and

dividing by the number of clusters95. Pertaining to mean cluster size however, the study



91 Barker, R.A. et al. “Verbal Fluency in Huntington’s Disease: A Longitudinal Analysis of Phonemic and Semantic Clustering and Switching.” Neuropsychologia, 2002; 40(8): 1277-84. Elsevier. Web. 31 Jul. 2012.

92 John, Sunila et al. “Qualitative Analysis of Clustering on Verbal Fluency in Young Adults.” Language in India, Jul. 2011; 11. Web. 31 Jul. 2012., Leggio, Maria Giuseppa et al. “Phonological Grouping is Specifically Affected in Cerebellar Patients: A Verbal Fluency Study.” J. Neurol. Neurosurg. Psychiatry, 2000; 69:102-106. BMS Publishing Group. Web. 31 Jul. 2012., Sherman, Elisabeth MS et al. A Compendium of Neuropsychological Tests. New York: Oxford University Press, 2006. Print.

93 Sherman, Elisabeth MS et al. A Compendium of Neuropsychological Tests. New York: Oxford University Press, 2006. Print., Troyer, A.K. “Normative Data for Clustering and Switching on Verbal Fluency Tasks.” Journal of Clinical and Experimental Neuropsychology, 2010; 22(3): 370-378. Web. 14 Jan 2013.

94 Barker, R.A. et al. “Verbal Fluency in Huntington’s Disease: A Longitudinal Analysis of Phonemic and

Semantic Clustering and Switching.” Neuropsychologia, 2002; 40(8): 1277-84. Elsevier. Web. 31 Jul. 2012.

95 Barker, R.A. et al. “Verbal Fluency in Huntington’s Disease: A Longitudinal Analysis of Phonemic and Semantic Clustering and Switching.” Neuropsychologia, 2002; 40(8): 1277-84. Elsevier. Web. 31 Jul. 2012., Sherman, Elisabeth MS et al. A Compendium of Neuropsychological Tests. New York: Oxford

22

“Qualitative Analysis of Clustering on Verbal Fluency in Young Adults” (John 2011) did not find

any significant correlation between mean cluster sizes and total number of words produced96.

On the other hand, other studies’ results show a close relation between clustering/switching

scores and the total number of words generated97. Also, the number of clusters for subjects can

be counted, or a cluster ratio can be calculated98. Cluster ratios are found by dividing the total

number of words generated by the number of clusters, creating a comparison between general

semantic/phonemic word scores and cluster scores99. When creating cluster scores, some

studies have suggested including repetitions and intrusions into these scores but not the overall

scores. Studies have also counted overlapping clusters, but not clusters within another

cluster100.

Switches are generally just counted as the sum of the number of switches/transitions

that occur during tests—that is, the ‘frequency’ of switches. Switches may be counted

separately based on whether they are switches between semantic or phonemic categories in

both semantic and phonemic fluency tests101.

The updated normative data demonstrating standard results reveals better overall

performance on verbal fluency tests over the recent past. Examiners should be aware,

however, that these raised norms/standards make the tests more sensitive and more likely that

people will be classified as impaired102.

University Press, 2006. Print.96 John, Sunila et al. “Qualitative Analysis of Clustering on Verbal Fluency in Young Adults.” Language in

India, Jul. 2011; 11. Web. 31 Jul. 2012.97 Baudu, C. et al. “Clustering and Switching Strategies in Verbal Fluency Tasks: Comparison Between

Schizophrenics and Healthy Adults.” J. Int. Neuropsycho. Soc., 1998; 4(6): 539-46. PubMed. Web. 31 Jul. 2012.

98 John, Sunila et al. “Qualitative Analysis of Clustering on Verbal Fluency in Young Adults.” Language in India, Jul. 2011; 11. Web. 31 Jul. 2012., Leggio, Maria Giuseppa et al. “Phonological Grouping is Specifically Affected in Cerebellar Patients: A Verbal Fluency Study.” J. Neurol. Neurosurg. Psychiatry, 2000; 69:102-106. BMS Publishing Group. Web. 31 Jul. 2012.

99 Leggio, Maria Giuseppa et al. “Phonological Grouping is Specifically Affected in Cerebellar Patients: A Verbal Fluency Study.” J. Neurol. Neurosurg. Psychiatry, 2000; 69:102-106. BMS Publishing Group. Web. 31 Jul. 2012.

100 Troyer, A.K. “Normative Data for Clustering and Switching on Verbal Fluency Tasks.” Journal of Clinical and Experimental Neuropsychology, 2010; 22(3): 370-378. Web. 14 Jan 2013.



23

Alternate Tests and Factors Affecting Test Outcomes

Examiners should be aware of general patterns occurring during verbal fluency tests.

Typically, people produce more words at the beginning of trials, although some are at first

flustered and struggle with ‘task initiation.’ Some neurologists have tried to study verbal fluency

by tracking the number of words said in fifteen second segments103. Additional data that can be

tracked includes subjects’ changes in speed of response, mental organization, and memory

abilities for verbal fluency tasks104.

The verbal fluency tests can be given in a variety of ways. A combination test can be

administered where a semantic and phonemic category are given—for instance, a subject has

to come up with animal names beginning with ‘s’105. Or, multiple semantic or phonemic

categories may be given; a subject can switch between, for example, animals and foods during

a semantic task, or the letters ‘s’ and ‘f’ during a phonemic task106.

Alternate types of fluency tests (than semantic or phonemic) are available as well. The

Homophonic Meaning Generation Tests asks subjects to provide multiple definitions for

homophones (ex. sun, son). The Excluded Letter Fluency Tasks asks subjects to create words

without a specific vowel, and the Uses for Common Objects Task ask subjects to generate

unusual tasks for everyday objects. Furthermore, ‘action’ fluency tests challenge subjects to

name verbs (activities people do).

A typical substitute for a verbal fluency task is a test of written word fluency. First used

by Thurstone in 1938, written word fluency tests have subjects tackle semantic and phonemic

tasks by writing answers down on paper. These tasks try to access language and executive

thinking in patients in a different way than semantic and phonemic tasks; these written word

fluency tests are, in fact, very sensitive to frontal lobe dysfunction and are good at predicting





24

damage to that area. Many times, no matter the format, verbal fluency tests are given multiple

times because they are a good tracker of change in patterns of thought in people’s brains107.

Generally, verbal fluency tests should be scored with acknowledgment of the ages,

genders, and levels of education of the subjects involved108. Formulas have even been

computed to accommodate for age and education related variance.

Age may have some effect on the outcome of verbal fluency tests. Reports have

suggested that semantic scores need more adjustment for age than phonemic tests.

Phonemics, for instance, improves during childhood, with especial growth when children are

between the ages of five and seven109. Verbal fluency then peaks in one’s thirties, and mild

decline is seen in ‘old age.’ When clustering and switching are involved, people who are

‘younger’ produce more words and switches during semantic fluency tests110. Older age seems

to correlate with larger cluster sizes, especially phonemic clusters, although the number of

switches and words generated drops111.

Conflicted information as to the effect of gender on verbal fluency tests exists. Some

studies report clustering and switching scores to be affected minimally by gender, yet other

studies report gender to not affect clustering abilities at all112. Executive speech tasks are said to

‘favor’ women, which implies women’s ability to do better on phonemic tasks (relying on

executive function). In fact, women are said to do better on phonemic fluency tasks because


108 Sherman, Elisabeth MS et al. A Compendium of Neuropsychological Tests. New York: Oxford University Press, 2006. Print., Tranel, Daniel. “Impaired Naming of Unique Landmarks is Associated with Left Temporal Polar Damage.” Neuropsychology, 2006; 20(1): 1-10. American Psychological Association. Print.


110 Troyer, AK. “Clustering and Switching as Two Components of Verbal Fluency: Evidence from Younger and Older Healthy Adults.” Neuropsychology, 1997; 11: 138-146. Baycrest. Web. 31 Jul. 2012.

111 Sherman, Elisabeth MS et al. A Compendium of Neuropsychological Tests. New York: Oxford University Press, 2006. Print., Troyer, AK. “Clustering and Switching as Two Components of Verbal Fluency: Evidence from Younger and Older Healthy Adults.” Neuropsychology, 1997; 11: 138-146. Baycrest. Web. 31 Jul. 2012.


25

they switch more, while men, clustering more, generate less words overall. Women have also

been speculated to do better perhaps because of ‘better memories’113.

Education may also have some effect on scores. Education is said to have a small effect

on clustering and switching scores114.

Memory has a role in verbal fluency as well. When comprehending speech in order to

understand a task, short term memory must hold onto words until sentences can be

interpreted, and research has seen that “working memory perception-actions loops are

identifiable for the different language components”115. Working memory also helps to keep

track of words already generated, preventing repetition116. In fact, the more complex the task,

the longer the information must be held in auditory short term memory117. Between

orthographic processing, based off visual cues, phonemic processing, based off auditory cues,

and semantic processing, based off understanding meaning, semantic processing helps memory

best because the additional analysis needed for semantics helps a person recall information118.

In fact, according to Baldo (2003), memory networks are the impetus responsible for

connecting words semantically119.

Attention given to verbal fluency tests has also been identified as important120. For

instance, during semantic fluency tests, subjects not giving the task their full attention will still

113 Bilar, WB et al. “Sex Differences in Clustering and Switching in Verbal Fluency Tasks.” J. Int. Neuropsychol. Soc., Jul 2006; 12(4): 502-9. PubMed. Web. 31 Jul. 2012.


115 Beaucousin, V. et al. “Meta-analyzing Left Hemisphere Language Area: Phonology, Semantics, and Sentence Processing.” Neuroimage, May 2006; 30(4): 1414-32. PubMed. Web. 30 Jul. 2012., Price, Cathy J. “The Anatomy of Language: A Review of 100 fMRI Studies Published in 2009.” Annals of the New York Academy of Sciences, 2912; 1191: 62-88. Print.



118 Barton, Emily A. “Levels of Processing: The Effects of Orthographic, Phonologic, and Semantic Processing on Memory.” Student Pulse, 2012. Web. 30 Jul. 2012.


120 Barker, R.A. et al. “Verbal Fluency in Huntington’s Disease: A Longitudinal Analysis of Phonemic and Semantic Clustering and Switching.” Neuropsychologia, 2002; 40(8): 1277-84. Elsevier. Web. 31 Jul. 2012., John, Sunila et al. “Qualitative Analysis of Clustering on Verbal Fluency in Young Adults.” Language in India, Jul. 2011; 11. Web. 31 Jul. 2012.

26

be able to generate answers, but their ability to do well is restricted121. In younger subjects in

particular, divided attention on tasks results in a decreased total number of words and a

decreased frequency of switching122.

Tests of verbal fluency are adjusted based on culture. For instance, Chinese culture does

not have the same semantic and phonemic norms as American culture, and so, to get accurate

test results, the language test would have to be readjusted to Chinese norms123.

Certain subjects are not eligible to be used in studies of verbal fluency because of

mental deficits. Therefore, before testing, subjects should be screened for initial intellectual

impairment and should not participate in the studies if deficits are not due to their current

lesions124. Subjects can also be screened for left language dominance (which is most typical) in

order to help control studies; testing for left hemispheric dominance can usually be done by

screening for right handed subjects125. Subjects with aphasia, or impaired comprehension, are

more likely to produce fewer words or have many errors; subjects with paraphasia, or people

who have lost the ability to speak correctly, should definitely be excluded from verbal fluency

studies126. Subjects with significant head injury should not be used because damage (especially

to the frontal lobes) could hurt the executive processes needed during verbal fluency tests;

data has shown performance on tests decreases as the severity of the head injury increases.

Also, mood and thought disorders—which have been correlated with cognitive slowing—create

distress in subjects, causing fluency scores to go down127.

Anatomy Concerning Verbal Fluency

121 Carlson, Synnove et al. “Attention and Semantic Processing During Speech: An fMRI Study.” Brain and Cognition Aug. 2012; 122(12): 114-119. ScienceDirect. Web. 30 Jul. 2012.

122 Troyer, AK. “Clustering and Switching as Two Components of Verbal Fluency: Evidence from Younger and Older Healthy Adults.” Neuropsychology, 1997; 11: 138-146. Baycrest. Web. 31 Jul. 2012.


124 Leggio, Maria Giuseppa et al. “Phonological Grouping is Specifically Affected in Cerebellar Patients: A Verbal Fluency Study.” J. Neurol. Neurosurg. Psychiatry, 2000; 69:102-106. BMS Publishing Group. Web. 31 Jul. 2012., Tranel, Daniel. “Impaired Naming of Unique Landmarks is Associated with Left Temporal Polar Damage.” Neuropsychology, 2006; 20(1): 1-10. American Psychological Association. Print.

125 Tranel, Daniel. “Impaired Naming of Unique Landmarks is Associated with Left Temporal Polar Damage.” Neuropsychology, 2006; 20(1): 1-10. American Psychological Association. Print.

126 “Paraphasia.” Dictionary.com, 2012. Web. 29 Jul. 2012., Sherman, Elisabeth MS et al. A Compendium of Neuropsychological Tests. New York: Oxford University Press, 2006. Print.


27

The brain is flexible and develops differently for different individuals. Because the brain

can develop differently, “anatomical selection of convergence zones…during learning…is

probability driven, flexible, and individual128.” With that information in mind, many different

regions have been examined in the brain for their connections to verbal fluency or speech in

general. Many regions, sometimes overlapping, are activated during the complex processes of

speech comprehension and production. Just speech production must go through the stages of

retrieving the correct words from memory, sequencing the words, planning articulation,

coordinating movements for speech to occur, and obtaining continuous feedback to monitor

speech during production129. And yet, for all these intricate processes, language perception, or

‘lexical exploration,’ and speech are primarily associated with the left hemisphere of the

brain130. Ninety percent of people are, in fact, left-hemisphere dominant for language, and

ninety-six percent are dominant for speech131. Like language, semantics and phonemics are

considered significantly lateralized the left hemisphere’s frontal, temporal, and parietal lobes,

although phonemics is generally more lateralized132. In more detail, verbal fluency tests have

been described as “frontal lobe tests” because when damage occurs to the frontal lobe, verbal

fluency frequently worsens; at the same time, other studies have described certain functions of

the language network as much larger and more complex than temporofrontal connections133.



130 Grabowska, Anna et al. “Phonological and Semantic Fluencies are Mediated by Different Regions of the Prefrontal Cortex.” Acta. Neurobiol. Exp., 2000; 60: 503-508. Web. 30 Jul. 2012., Price, Cathy J. “The Anatomy of Language: A Review of 100 fMRI Studies Published in 2009.” Annals of the New York Academy of Sciences, 2912; 1191: 62-88. Print., Snell, Richard S. Clinical Neuroanatomy for Medical Students. Philadelphia: Lippincott-Raven Publishers, 1997. Print.

131 Baciu, Monica et al. “Hemispheric Predominance Assessment of Phonology and Semantics: A Divided Visual Field Experiment.” Brain and Cognition, 2006; 61: 298-304. Elsevier. Web. 30 Jul. 2012., Badewien, Meike. “Differential Prefrontal and Frontotemporal Oxygenation Patterns During Phonemic and Semantic Verbal Fluency.” Neuropsychologia, June 2012; 50(7): 1565-1569. Elsevier and ScienceDirect. Web. 31 Jul. 2012., Snell, Richard S. Clinical Neuroanatomy for Medical Students. Philadelphia: Lippincott-Raven Publishers, 1997. Print.

132 Baciu, Monica et al. “Hemispheric Predominance Assessment of Phonology and Semantics: A Divided Visual Field Experiment.” Brain and Cognition, 2006; 61: 298-304. Elsevier. Web. 30 Jul. 2012., Badewien, Meike. “Differential Prefrontal and Frontotemporal Oxygenation Patterns During Phonemic and Semantic Verbal Fluency.” Neuropsychologia, June 2012; 50(7): 1565-1569. Elsevier and ScienceDirect. Web. 31 Jul. 2012.

133 Beaucousin, V. et al. “Meta-analyzing Left Hemisphere Language Area: Phonology, Semantics, and Sentence Processing.” Neuroimage, May 2006; 30(4): 1414-32. PubMed. Web. 30 Jul. 2012., Duffau, Hugues and Martiz-Gasser, Sylvie. “Evidence of a Large-Scale Network Underlying Language Switching:

28

One theory is that interactions occur between the dorsolateral prefrontal cortex and

temporal cortex for verbal fluency, and that the frontal cortex searches and retrieves

information from the temporal regions when necessary. The theory points towards an

associative component to verbal fluency, where semantic organization of memory occurs, and

towards an executive component, where responses are initiated134. Certain connections in the

brain help to support this theory. Broca’s speech area, for instance, in the inferior frontal gyrus

is connected to the speech area of Wernicke—an area for reading and understanding sentences

—in the temporal gyrus135. Another theory is Damasio’s convergence zones. This theory paints

out the brain like a map with many interconnecting areas. According to this theory, the

prefrontal cortexes call up accumulated experience and other ideas136. Mental images to be

called up come from ‘sensory’ cortices and association cortices hold memory to be called up137.

Another interesting theory concerning language involves the study of genes. Mutations in the

FOXP2 expressive gene have been identified with problems processing words grammatically,

understanding complex sentence structures, and forming intelligible sounds. The FOXP2 has

also been associated with brain abnormalities as well. Abnormalities caused by FOXP2

mutations in the caudate nuclei (connected to the frontal lobe) and Broca’s area in the frontal

lobe signifies the potential importance of the frontal lobe in relation to language138.

Other brain regions are involved with verbal fluency as well. Some studies have found

correlations between verbal fluency and cerebellum (bilaterally) because the cerebellum is

connected with the left inferior frontal gyrus and left lateral temporal cortex, and when

cerebellar activity is decreased, repetitions increase139. Connections between various forms of

A Brain Stimulation Study.” J. Neurosurg, 2009; 111: 729-732. Joint Media News Service. Web. 30 Jul. 2012., Grabowska, Anna et al. “Phonological and Semantic Fluencies are Mediated by Different Regions of the Prefrontal Cortex.” Acta. Neurobiol. Exp., 2000; 60: 503-508. Web. 30 Jul. 2012.


135 Flaherty, Alice W. and Rost, Natalia S. The Massachusetts General Hospital Handbook of Neurology. Philadelphia: Lippencott Williams & Wilkins, 2007. Print., Snell, Richard S. Clinical Neuroanatomy for Medical Students. Philadelphia: Lippincott-Raven Publishers, 1997. Print.

136 Dennett, Daniel C. “Review of Demasio, Descartes’ Error.” Times Literary Supplement, Aug. 1995: 3-4. Tufts University. Web. 22 Aug. 2012.

137 Damasio, Antonio and Meyer, Kaspar. “Convergence and Divergence in a Neural Architecture for Recognition and Memory.” Trends in Neuroscience, July 2009; 32(7): 376-382. SciVerse. Web. 22 Aug. 2012.

138 MacAndrew, Alec. “FOXP2 and the Evolution of Language.” Alec’s Evolution Pages, 2003. Web. 2 Sept. 2012.139 Ali, Nilufa et al. “Structural Correlates of Semantic and Phonemic Fluency Ability in First and Second

Languages.” Cereb. Cortex, Nov. 2009; 19(11): 2690-2698. NCBI. Web. 30 Jul. 2012., Duffau, Hugues and

29

verbal fluency and the frontal, temporal, and parietal cortexes have been made as well140. The

dorsolateral prefrontal cortex in particular, found in the middle frontal gyrus, helps with

movement control in addition to thought, cognition, planning, and behavior. Broca’s speech

area and the overall lateral premotor cortex are found in the inferior frontal gyrus and assist

with speech, movement, and planning141. More specifically, prelexical speech production, the

period during speech interpretation when information is still being interpreted and semantic

recognition has not yet occurred, has been reported in the bilateral superior temporal gyri142.

‘Meaningful’ speech has been seen in the middle and inferior temporal cortexes, and speech

comprehension has been seen in the bilateral superior temporal lobe. Speech production, the

process where conceptual ideas are linked to articulation, has additionally been noted in the

left middle frontal cortex, as well as the left anterior insula, bilateral head of caudate, anterior

cingulate, motor cortex, and cerebellum143. Articulatory planning has been seen to take place in

the left anterior insula, predicting sequencing of events has been seen in the dorsal and ventral

pars opercularis of the inferior frontal lobe, initiation and execution of speech has been seen in

the motor cortex, and suppressing unintended responses has been seen in the anterior

cingulate and bilateral head of caudate nuclei (these caudate nuclei can be found near basal

nuclei, on the medial side of the nerve fibers called the corona radiata)144. Actual articulation is

seen bilaterally in the motor and premotor cortex, the cerebellum, the supplementary motor

area, the superior temporal gyri, the temporo-parietal cortices, and the anterior insula, with

Martiz-Gasser, Sylvie. “Evidence of a Large-Scale Network Underlying Language Switching: A Brain Stimulation Study.” J. Neurosurg, 2009; 111: 729-732. Joint Media News Service. Web. 30 Jul. 2012., Leggio, Maria Giuseppa et al. “Phonological Grouping is Specifically Affected in Cerebellar Patients: A Verbal Fluency Study.” J. Neurol. Neurosurg. Psychiatry, 2000; 69:102-106. BMS Publishing Group. Web. 31 Jul. 2012.

140 Baldo, J. et al. “Role of Frontal Versus Temporal Corte in Verbal Fluency as revealed by Voxel-Based Lesion Symptom Mapping.” J. Int. Neuropsychol. Soc., Nov. 2006; 12(6): 896-900. PubMed. Web. 30 Jul. 2012., Price, Cathy J. “The Anatomy of Language: A Review of 100 fMRI Studies Published in 2009.” Annals of the New York Academy of Sciences, 2912; 1191: 62-88. Print.

141 Blumenfeld, Hal. Neuroanatomy Through Clinical Cases. Sunderland: Sinauer Associates Inc., 2002. Print.142 “Prelexical.” Dictionary.com, 2012. Web. 29 Jul. 2012. Price, Cathy J. “The Anatomy of Language: A

Review of 100 fMRI Studies Published in 2009.” Annals of the New York Academy of Sciences, 2912; 1191: 62-88. Print.,



30

increased activation seen when forming novel or unfamiliar words145. Means for syntactic

processing, or sequencing words, finding patterns in language, and analyzing grammar, has

been seen in the left pars opercularis and left dorsal pars opercularis146. Likewise, prosodic

processing, or realizing patterns of stress and intonation from speech, is done in the superior

temporal lobes; emotional prosody involves the amygdala. Word retrieval, as well as generating

words semantically or phonemically related, can take place as broadly as the left inferior and

middle frontal gyri, spanning the pars opercularis (specifically the left dorsal and left ventral

pars opercularis), pars triangularis, and inferior frontal sulcus147.

Other important areas that especially relate to speech and cognition also exist in the

brain as association areas. They can be defined as certain areas mapped out by Brodmann’s

Cytoarchitectonic Areas148. The prefrontal association cortex, anterior to the precentral gyrus

and found in the superior, middle frontal gyri, inferior frontal gyrus, orbital gyri, and medial

frontal lobe, functions to help with thought, behavior, cognition, movement, and planning149.

Both the parietal-temporal-occipital association cortex (middle temporal visual area), found in

the middle and inferior temporal gyri at the junction of temporal/occipital lobes, (as well as the

inferior parietal lobes or angular and supramarginal gyrus), are used for perception, vision,

reading, and speech.150. In addition, an area of the parietal lobe known as the Somesthetic

Association Area “not only receives information concerning the size and shape of an object but

also relates this to past sensory experiences, so that the information may be interpreted and

recognition occurs.” If this association area is not limited to having to see objects, it might be a

powerful force in memory retrieval and perhaps in word retrieval. This theory may be


146 Beaucousin, V. et al. “Meta-analyzing Left Hemisphere Language Area: Phonology, Semantics, and Sentence Processing.” Neuroimage, May 2006; 30(4): 1414-32. PubMed. Web. 30 Jul. 2012., Price, Cathy J. “The Anatomy of Language: A Review of 100 fMRI Studies Published in 2009.” Annals of the New York Academy of Sciences, 2912; 1191: 62-88. Print., “Syntax.” Dictionary.com, 2012. Web. 29 Jul. 2012.





31

strengthened by the fact that other association cortexes, like the auditory association cortex,

have been found to be used for the interpretation of sounds151.

Mixed, although similar, results have reported where semantic processes occur in the

brain. Many times, semantic processing has been associated with the temporal lobe (especially

the left inferior temporal cortex), probably because “familiarity [of information] results in more

successful top-down predictions from left front regions that stabilize acoustic processing in the

left temporal lobe more than the right temporal lobe152.” In other words, known information

can be taken from the left temporal lobe, which is used for word retrieval, most successfully

when top-down processing occurs153. Different parts of the temporal lobe are activated for

specific semantic categories: The left temporal polar region is important for the retrieval of

proper names (names, landmarks), the medial temporal lobe has been associated with

autobiographical memories, and right lateralization in the temporal lobe is seen when semantic

answers are automated (ex. listing off days of the week), although none of these types of

semantic processing are generally used during semantic fluency tests154. The anterior temporal

lobe, part of the association cortex, is particularly interesting, as it plays a role in the storage

and recall of sensory experience, which may be related to semantic tasks155. One study by

Aylward et al. found that the anterior temporal lobe was critical for category-specific naming

and recognition, with the nondominant anterior temporal lobe binding sensory information


152 Ali, Nilufa et al. “Structural Correlates of Semantic and Phonemic Fluency Ability in First and Second Languages.” Cereb. Cortex, Nov. 2009; 19(11): 2690-2698. NCBI. Web. 30 Jul. 2012., Price, Cathy J. “The Anatomy of Language: A Review of 100 fMRI Studies Published in 2009.” Annals of the New York Academy of Sciences, 2912; 1191: 62-88. Print.


154 Baldo, Juliana et al. “Pervasive Influence of Semantics in Letter and Category Fleuncy: A Multidimensional Approach.” Brain and Language, 2003, Academic Press. Web. 31 Jul. 2012., Baldo, J. et al. “Role of Frontal Versus Temporal Corte in Verbal Fluency as revealed by Voxel-Based Lesion Symptom Mapping.” J. Int. Neuropsychol. Soc., Nov. 2006; 12(6): 896-900. PubMed. Web. 30 Jul. 2012., Moscovitch, Morris and Sheldon, Signy. “The Nature and Time-Course of Medial Temporal Lobe Contributions to Semantic Retrieval: An fMRI Study on Verbal Fluency.” Hippocampus, June 2012; 22(6): 1451-1466. Wiley Periodicals. Web. 31 Jul. 2012., Price, Cathy J. “The Anatomy of Language: A Review of 100 fMRI Studies Published in 2009.” Annals of the New York Academy of Sciences, 2912; 1191: 62-88. Print., Tranel, Daniel. “Impaired Naming of Unique Landmarks is Associated with Left Temporal Polar Damage.” Neuropsychology, 2006; 20(1): 1-10. American Psychological Association. Print.


32

into conceptual perceptions and the dominant temporal lobe linking thoughts to verbal

labels156. At the same time, for speech comprehension, the left frontal lobe has more

consistently been activated than the left temporal lobe (the frontal lobe is more lateralized).

The semantic processing network, usually identified as left lateralized, becomes more

detailed than simply the temporal lobe157. It has also been said to be focused on Heschl’s gyrus,

an area for auditory perception158. In particular, semantic retrieval has been illustrated to be

involved with the left angular gyrus and pars orbitalis, as well as the bilateral mid to anterior

superior temporal lobe159. Semantic storage and retrieval occurs in the left pars orbitalis, the

entire inferior frontal gyrus, ventral/ventromedial/right ventromedial/dorsal medial/left and

right dorsolateral prefrontal cortex, posterior inferior parietal lobe, middle temporal gyrus,

parahippocampal gyri, the posterior cingulate gyrus, and has been seen rarely in the right

frontal and temporal lobes160. Semantic processing, when interpreting conflicting or confusing

information, seems to be activated in the right inferior frontal lobe, but activated in temporal

and parietal lobes when the information presented is comprehensible. For example, when

making semantic ‘decisions’ on whether words/sentences are sensible, activation occurs in the

superior frontal gyrus161. When subjects are given sentences to semantically interpret,

156 Aylward, Elizabeth et al. “Category-specific naming and recognition deficits in temporal lobe epilepsy surgical patients.” Neuropsychologia, 2008: 46(5):1242-1255. Elsevier and SciVerse. Web. 22 Aug. 2012.

157 Badewien, Meike. “Differential Prefrontal and Frontotemporal Oxygenation Patterns During Phonemic and Semantic Verbal Fluency.” Neuropsychologia, June 2012; 50(7): 1565-1569. Elsevier and ScienceDirect. Web. 31 Jul. 2012.


159 Baciu, Monica et al. “Hemispheric Predominance Assessment of Phonology and Semantics: A Divided Visual Field Experiment.” Brain and Cognition, 2006; 61: 298-304. Elsevier. Web. 30 Jul. 2012., Price, Cathy J. “The Anatomy of Language: A Review of 100 fMRI Studies Published in 2009.” Annals of the New York Academy of Sciences, 2912; 1191: 62-88. Print.

160 Ali, Nilufa et al. “Structural Correlates of Semantic and Phonemic Fluency Ability in First and Second Languages.” Cereb. Cortex, Nov. 2009; 19(11): 2690-2698. NCBI. Web. 30 Jul. 2012., Baciu, Monica et al. “Hemispheric Predominance Assessment of Phonology and Semantics: A Divided Visual Field Experiment.” Brain and Cognition, 2006; 61: 298-304. Elsevier. Web. 30 Jul. 2012., Beaucousin, V. et al. “Meta-analyzing Left Hemisphere Language Area: Phonology, Semantics, and Sentence Processing.” Neuroimage, May 2006; 30(4): 1414-32. PubMed. Web. 30 Jul. 2012., Grabowska, Anna et al. “Phonological and Semantic Fluencies are Mediated by Different Regions of the Prefrontal Cortex.” Acta. Neurobiol. Exp., 2000; 60: 503-508. Web. 30 Jul. 2012., Price, Cathy J. “The Anatomy of Language: A Review of 100 fMRI Studies Published in 2009.” Annals of the New York Academy of Sciences, 2912; 1191: 62-88. Print.


33

activation is seen in the anterior and posterior left middle temporal gyrus, bilateral anterior

temporal poles, left angular gyrus, and posterior cingulate and precuneus. These areas,

naturally, are associated with semantic processing, although a majority of focus is centered on

the anterior and posterior parts of the middle temporal gyrus. Interestingly, when subjects have

been given incomprehensible sentences to try to interpret, inferior frontal regions are

activated, along with the posterior planum temporale and ventral supramarginal gyrus. This

process has been associated with predicting sentences outcomes; in other words, using prior

knowledge of ‘semantic associations,’ word sequences, and articulation to predict or make

sense of sentences. Accordingly, as sentence comprehension difficulty rises, so does activation

in the planum temporale and ventral/dorsal supramarginal gyrus; these two regions reduce

errors that become more likely with phonemic and semantic restraints. The left/left dorsal pars

opercularis (part of the activated inferior frontal regions) is also activated, even though this

area is unspecific to semantics162. In a situation where semantic processing is occurring, but a

subject’s full attention is not been given to auditory stimuli, activation is seen in the temporal

gyrus163.

Phonemic fluency is involved with parts of the brain similar and dissimilar from those

involved with semantic fluency. Phonemic is first and foremost associated with the frontal lobe

because of the strategic word retrieval involved in the process164. For example, the same areas

needed for word retrieval (the inferior/left inferior and middle frontal gyri) are activated during

phonemic tasks (with even greater activation than during semantic tests)165. Specifically,

phonemic fluency has been observed to decrease with lesions in the dorsolateral region of the


163 Carlson, Synnove et al. “Attention and Semantic Processing During Speech: An fMRI Study.” Brain and Cognition Aug. 2012; 122(12): 114-119. ScienceDirect. Web. 30 Jul. 2012.

164 Ali, Nilufa et al. “Structural Correlates of Semantic and Phonemic Fluency Ability in First and Second Languages.” Cereb. Cortex, Nov. 2009; 19(11): 2690-2698. NCBI. Web. 30 Jul. 2012., Baldo, J. et al. “Role of Frontal Versus Temporal Corte in Verbal Fluency as revealed by Voxel-Based Lesion Symptom Mapping.” J. Int. Neuropsychol. Soc., Nov. 2006; 12(6): 896-900. PubMed. Web. 30 Jul. 2012.

165 Baciu, Monica et al. “Hemispheric Predominance Assessment of Phonology and Semantics: A Divided Visual Field Experiment.” Brain and Cognition, 2006; 61: 298-304. Elsevier. Web. 30 Jul. 2012., Beaucousin, V. et al. “Meta-analyzing Left Hemisphere Language Area: Phonology, Semantics, and Sentence Processing.” Neuroimage, May 2006; 30(4): 1414-32. PubMed. Web. 30 Jul. 2012., Sherman, Elisabeth MS et al. A Compendium of Neuropsychological Tests. New York: Oxford University Press, 2006. Print.

34

prefrontal cortex, as well as the anterior region166. Other studies have shown phonemic fluency

to be linked to the superior temporal lobe, inferior parietal (supramarginal gyrus), pre-

supplementary motor area, and head of caudate (bilaterally)167. Phonemic fluency’s connection

to the pre-supplementary motor area may be because of the pre-SMA’s functions involving

planning movement and guiding the selection of words—two tasks needed for phonemic

fluency. The head of caudate is associated with phonological learning, processing ambiguous

words, and detecting phonological abnormalities168.

A few studies are beginning to look at where clustering and switching strategies may

occur in the brain. Generally, “decreased clustering has been related to temporal lobe

disturbance, while switching implicates frontal functioning, although some inconsistencies in

this pattern have been noted169.” In other words, the temporal lobe is critical to a subject’s

ability to cluster information; the frontal lobe and its connections to other areas of the brain

are needed for switching170. Temporal lobe data and its role in verbal fluency, however, has

been noted to be a bit less consistent In a few more specific studies, decreased switching

abilities have been seen when lesions occupy the left-dorsolateral frontal lobe or superior-

166 Badewien, Meike. “Differential Prefrontal and Frontotemporal Oxygenation Patterns During Phonemic and Semantic Verbal Fluency.” Neuropsychologia, June 2012; 50(7): 1565-1569. Elsevier and ScienceDirect. Web. 31 Jul. 2012., Grabowska, Anna et al. “Phonological and Semantic Fluencies are Mediated by Different Regions of the Prefrontal Cortex.” Acta. Neurobiol. Exp., 2000; 60: 503-508. Web. 30 Jul. 2012.

167 Ali, Nilufa et al. “Structural Correlates of Semantic and Phonemic Fluency Ability in First and Second Languages.” Cereb. Cortex, Nov. 2009; 19(11): 2690-2698. NCBI. Web. 30 Jul. 2012., Baciu, Monica et al. “Hemispheric Predominance Assessment of Phonology and Semantics: A Divided Visual Field Experiment.” Brain and Cognition, 2006; 61: 298-304. Elsevier. Web. 30 Jul. 2012.



170 Baldo, Juliana et al. “Pervasive Influence of Semantics in Letter and Category Fleuncy: A Multidimensional Approach.” Brain and Language, 2003, Academic Press. Web. 31 Jul. 2012., Barker, R.A. et al. “Verbal Fluency in Huntington’s Disease: A Longitudinal Analysis of Phonemic and Semantic Clustering and Switching.” Neuropsychologia, 2002; 40(8): 1277-84. Elsevier. Web. 31 Jul. 2012., John, Sunila et al. “Qualitative Analysis of Clustering on Verbal Fluency in Young Adults.” Language in India, Jul. 2011; 11. Web. 31 Jul. 2012., Troyer, AK. “Clustering and Switching as Two Components of Verbal Fluency: Evidence from Younger and Older Healthy Adults.” Neuropsychology, 1997; 11: 138-146. Baycrest. Web. 31 Jul. 2012., Troyer, Angela K. “Clustering and Switching on Verbal Fluency: The Effects of Focal Frontal and Temporal Lobe Lesions.” Neuropsychologia, June 1998; 36(1): 499-504. Elsevier and ScienceDirect. Web. 31 Jul. 2012.

35

medial frontal lobe171. Switching has not been seen in the prefrontal regions when semantic

answers are automated (ex. months of the year, days of the week)172.

Lesions & Lesion Studies

A lesion is classified as an injury or wound to the body, and more specifically, is an

abnormal structure such as a tumor173. Lesions are harmful because, at least in some instances,

they can expel cerebrospinal fluid from cranial cavities. Veins become compressed when this

happens, causing intracranial pressure which the brain tries to solve by putting out more

cerebrospinal fluid. A cycle forms, usually one which causes lesion patients much pain174.

Lesions in the brain can hurt the structure or cause neuroanatomical segregation, separating

parts of the brain from their usual connections175.

Brain tumors are a common lesion also known as an intracranial tumor. Brain tumors

can be primary, new tumors that form in the brain, or metastases, tumors that spread

systematically to the brain. A lesion resulting from a removed brain tumor is known as a focal

lesion. Tumors damage the brain and can cause seizures, dementia, and paralysis. They are

thought to form as a result as a result of a combination of environmental factors and more

rarely because of genetic abnormalities. Even more, brain tumors pose a sizable threat to

society; in 2001, the American Cancer Society found 17,200 primary brain tumor cases to occur

which killed about 13,100 people176. By 2008, the American Cancer Society found the total

prevalence of brain and nervous systems cancers to be at 129,000 cases177.

Lesion studies compare lesion patients to healthy controls to see, when lesions damage

certain parts of the brain, how those areas are affected. When the subjects with lesions

experience, for instance, impaired top-down processing, the experimenter can discern if the

171 Troyer, Angela K. “Clustering and Switching on Verbal Fluency: The Effects of Focal Frontal and Temporal Lobe Lesions.” Neuropsychologia, June 1998; 36(1): 499-504. Elsevier and ScienceDirect. Web. 31 Jul. 2012.

172 Amunts K. “Within-task Switching in the Verbal Domain.” Neuroimage, Nov. 2003; 20. PubMed. Web. 31 Jul. 2012.

173 “Lesion.” Dictionary.com, 2012. Web. 12 Jul. 2012., Snell, Richard S. Clinical Neuroanatomy for Medical Students. Philadelphia: Lippincott-Raven Publishers, 1997. Print.



176 DeAngelis, Lisa M. Intracranial Tumors. Martin Dunitz Ltd, 2002. Print.177 “Cancer Prevalence: How Many People Have Cancer?” American Cancer Society, 2012. Web. 24 Aug. 2012.

36

location where their lesions are is an area imperative to speech178. For example, in the study

“Impaired Naming of Unique Landmarks is Associated with Left Temporal Polar Damage,” to see

what temporal regions are important to retrieving proper nouns, lesion patients’ naming scores

(dependent variable) were correlated with their lesion locations (independent variable). When

compared against healthy patients, impaired name retrieval occurred for patients with lesions

in the left temporal lobe, allowing experimenters to conclude that the left temporal lobe is

needed for proper noun retrieval179.

Already, lesion studies have helped discern what functions certain parts of the brain

have. Lesions in the motor speech area of Broca result in expressive aphasia, although subjects

can still think of and understand words. If a lesion occurs in the speech area of Wernicke,

experimenters have observed that subjects cannot understand words—the subjects have

receptive aphasia. A lesion in the secondary auditory area can result in an inability to interpret

sounds, and lesions in the prefrontal cortex can lead to a loss of intelligence as well as deficits in

“associating abstract ideas, judgment, emotional feeling, and personality180.”

Lesion studies are the preferable way to understand what parts of the brain are critical

for certain tasks. Lesion studies are especially important to studying verbal fluency in particular.

fMRI studies of verbal fluency, for instance, can be affected negatively by subjects’ mouth

movements181. Lesion studies, using standard imaging (MRI) are more useful for obtaining

accurate data182. Lesion studies are also preferable because although lesion sizes are often

compared within a study, research has shown that the type of lesion in the brain does not

significantly affect test outcomes183.






183 Price, Cathy J. “The Anatomy of Language: A Review of 100 fMRI Studies Published in 2009.” Annals of the New York Academy of Sciences, 2912; 1191: 62-88. Print., Tranel, Daniel. “Impaired Naming of Unique Landmarks is Associated with Left Temporal Polar Damage.” Neuropsychology, 2006; 20(1): 1-10. American Psychological Association. Print.

37

Figure 4184

Research Questions

1. Which brain region(s) containing focal lesions result in the comparatively lowest total

word generation scores for categorization verbal fluency testing?

2. Which brain region(s) containing focal lesions result in the comparatively lowest total

word generation scores for letter verbal fluency testing?

184 MRI of the Brain following gadolinium demonstrating enhancement of MS lesions. 2012. University of

Maryland Medical Center. The Maryland Center for Multiple Sclerosis. Image. 13 Aug. 2012.

38

3. Which brain region(s) containing focal lesions result in the comparatively lowest scores

for clustering during categorization and letter verbal fluency testing?

4. Which brain region(s) containing focal lesions result in the comparatively lowest scores

for switching during categorization and letter verbal fluency testing?

Hypotheses

1. Focal lesions in the left temporal lobe will result in the comparatively lowest total word

generation scores for categorization verbal tests.

2. Focal lesions in the left frontal lobe will result in the comparatively lowest total word

generation scores for letter verbal fluency tests.

3. Focal lesions in the temporal lobes bilaterally will result in the comparatively lowest

scores for clustering during categorization and letter verbal fluency tasks.

4. Focal lesions in the left frontal lobe will result in the comparatively lowest scores for

switching during categorization and letter verbal fluency tests.

Materials

1. (Access to) Froedtert Medical Hospital’s adult brain lesion database

2. (Access to) research materials (i.e. Encyclopedias, dictionaries)

3. Copies of subjects’ Adult Brain Tumor Coding Sheets

4. Copies of subjects’ verbal fluency tests

5. Scoring criteria for classifying semantic and phonemic clusters and switching

during both categorization and letter fluency tasks (Created by experimenter)

6. Subject criteria for participating in the study (Created by experimenter)

7. Subjects’ data collection sheets (Created by experimenter)

Method

Subjects

A total of 82 subjects were used in this study. Of those, 46 were male and 36 were

female. The mean age for subjects was approximately 53 and the average year of education

39

was approximately 14. For the 82 subjects, 27 left frontal cases were used, 19 right frontal

cases were used, 14 left temporal cases were used, and 22 right temporal cases were used.

At the time of their verbal fluency testing, each subject had a focal brain lesion resulting

from surgery that removed a brain tumor. Information about subjects, all de-identified with an

ID number and containing given consent to be part of Froedtert’s research, was collected from

Froedtert Hospital’s forms known as Adult Brain Tumor Coding Sheets.

Subjects had to be between ages 18 and 89 and had to be right-handed. Subjects with

special education could not be used because they may not have been able to perform as well

on the verbal fluency tests, just as subjects whose first language is not English did not have their

data included in the study as those subjects might not have been as familiar with English words

for the tasks.

Regarding tumors, subjects could only have a primary (or potentially a single metastatic)

tumor; subjects could only have a tumor limited specifically to the right or left frontal or

temporal lobe. By making sure subjects had one tumor restricted to a definite area, the

possibility of another tumor affecting scores was made obsolete. All tumor grades were used in

the initial data analysis; 4 subjects had a tumor grade of 1, 18 subjects had a tumor grade of 2,

15 subjects had a tumor grade of 3, 34 subjects had a tumor grade of 4, and 11 subjects had no

or an unknown tumor grade.

Medically, subjects could not have a preexisting neurological illness or traumatic brain

injury which might have hurt their ability to perform proficiently on the verbal fluency tasks.

Patients, although having been tested after receiving surgery to remove their tumors (leaving

focal lesions), did not receive radiation or chemotherapy at the time of their baseline testing,

which was the testing used to evaluate subjects in the study.

During neurological testing, if subjects were cited for giving variable or poor effort or for

malingering, they were discarded from the study as well, since their efforts would be an

inaccurate reflection of their abilities on the verbal fluency tests.

Semantic Scoring Criteria

A specific set of criteria was used during subjects’ semantic verbal fluency test, where

subjects were given a minute to list as many animals as possible. Animals were grouped

40

semantically by location, defined as the same biome in the same region. For instance, both

giraffes and zebras live in the savannahs (biome) of Africa (region) so they would be counted as

a semantic cluster. Animals were also grouped by domestication, making farm animals or pet

animals potential clusters. Zoological category was a final way to group animals. Animals were

clustered in relation to how close they were evolutionarily to mammals, the group occurring

most frequently and with the greatest variety among animals listed. Therefore, invertebrates

were all grouped together, but the phylum Chordata was grouped by class (i.e. bird, reptile,

amphibian etc.; chordates osteichthyes and chondrichthyes were counted as one class).

Mammals, however, were classified by family (i.e. Felidae, Canidae). Determining animal

clusters could be done with the use of an encyclopedia to find animal location and zoological

categorization.

Semantic scoring criteria during letter verbal fluency tasks was different than for

semantic tasks since, during letter tasks, subjects could name any words beginning with the

specific letters F, A, and S or C, F, and L in three respective trials. To be counted as a cluster of

related words, words must have been related under a broader category (ex. soccer and softball

are both sports), defined as similar locations (ex. different rooms of a house), found in the same

location or used in the same place (ex. items used in an office), used for similar purposes (ex.

tools in a toolbox), defined as similar abstract concepts (ex. fear and frightened both relate to

being afraid), defined as synonyms (ex. below, beneath), or defined as words where one word

fits under the definition of the other (ex. a spoon is a type of silverware, therefore silverware

fits under the definition of spoon). Determining letter clusters could be done with the aid of a

dictionary to check the precise definitions of words.

Phonemic Scoring Criteria

Phonemic scoring criteria remained consistent across semantic and letter fluency tests

with few exceptions. For semantic tasks, words that began with the same letter were counted

as a cluster; since words in the letter tasks automatically began with the same first letter, they

were counted as a cluster if the words began with the first two letters. For both tasks, words

ending in the same (vowel) sound, such as –able or –ion, were counted as clusters. Words

ending in a vowel making a sound, for instance the –a as in zebra and hyena, would be

41

considered words ending in the same sound as well. Words that rhymed were considered

clusters, as were words differing only by one vowel or vowel sound between constants, such as

fin and fun; words that were homophones, like sew and so, were considered clusters.

Switching Criteria

One switch for both semantic and letter verbal fluency tasks would be counted if two

clusters (of two or more words) were adjacent to each other, if the last word(s) of one cluster

began the next cluster, or if one cluster was within another cluster.

Additional Notes

During the scoring for both semantic and letter verbal fluency tests, words were not

counted if they were proper nouns (which are not generated in the same region as the brain as

other words and therefore could not be controlled if considered in the study), prefixes/suffixes

(not full words), nonexistent words, or repetitions. Repetitions in particular may have been part

of clusters, but were not counted as such in order to remain consistent with the semantic/letter

fluency score given for the total number of words generated. Therefore, no clusters could be

made containing or “skipping” over repetitions; this measure also checked for only scoring for

novel word generation in subjects.

Data Collection

For each subject, a total of 35 scores were collected. A total word score was gathered,

which was the total words generated in the task. Then, each subject’s semantic and phonemic

clusters were found (separately). For each type of cluster, an average size of the clusters, total

number of clusters, and the number of switches between clusters were found. These seven

data points were repeated four times, for the categorization of animals task, and for each of the

three letter tasks. A combination score was also generated for the three letter tasks, with their

overall total score, average cluster sizes, total cluster number, and total switches number being

found respectively for both semantically and phonemically. When processing data, the

combination score for the letter tasks was used. In addition to these 35 scores, Froedtert

42

provided norms based on age for the total word scores for the categorization and letter tasks to

be compared against; (note that although these norms were collected, they were not used in

the final data analysis as no significant differences in age across subject groups was found).

Procedure

I. Data Collection

A. Potential subjects were found in Froedtert Medical Hospital’s brain lesion

database based on if they possessed a lesion in the left frontal, right frontal, left

temporal, or right temporal lobe.

B. Potential subjects had a “background check” run on them to make sure they fit

all the criteria to be included in the study (see “Subjects” above).

C. Subjects eligible to be in the study had their basic information and their verbal

fluency tests copied and de-identified.

II. Data Scoring

A. A data collection form was matched with each subject to collect information for

that subject.

B. The scorer first reviewed the subject’s categorization verbal fluency test,

marking any time clusters appeared according to the scoring criteria.

1. Semantic scoring used the “Semantic Scoring Criteria” above to classify

clusters.

a. Once all clusters were identified and verified by sources such as an

encyclopedia, the number of clusters was totaled and the average size of

clusters was found.

b. Using the clusters identified, the number of switches occurring between

clusters was found (see “Switching Criteria” above).

2. Phonemic scoring for category fluency tests used the “Phonemic Scoring

Criteria” above to classify clusters. The process of phonemic scoring followed

the steps of 1(a) and 1(b) above to classify clusters and switches.

43

C. The scorer reviewed the subject’s three letter fluency tests, marking any time

clusters appeared according to the scoring criteria.

1. Steps B(1) and B(2) in full were repeated for semantic and phonemic scoring,

using the adjusted scoring criteria for phonemic classification.

III. Data Processing

A. Data checking—After finishing data scoring, all data was reviewed to make sure

that it was scored as accurately as possible and fit the scoring criteria.

B. Data entry

1. Data was entered into an Excel spreadsheet, along with basic subject

information including: subject ID numbers, tumor grade, age, years of

education, gender, ethnicity, and lesion location.

2. Data was checked again to make sure that no information was missing and

that no subjects had been repeated in the data set.

3. The combination score was created using Excel to combine each subjects’

scores from the three letter fluency tests.

C. Data analysis

1. SPSS was used to run multivariate analysis of variances on data.

2. Descriptives were run to see if groups differed by age or education.

3. When ANOVAs revealed significant main effects, pairwise comparisons were

studied to see which brain regions created significance.

4. T-tests were used to further investigate significant main effects between

brain regions; Levene’s Test for Equality of Variances was used to determine

if equal variances would be assumed on the T-test for equality of means.

Results

Results were found using multivariate analyses of variance and pairwise comparisons.

Significant results were furthered studied using T-tests for equality of means (p < 0.05). When

Levene’s Test for Equality of Variances showed no significance, a minimal degree of error was

presumed and the p value with equal variances assumed was used. When Levene’s Test for

44

Equality of Variances was significant, the p value with equal variances not assumed was used

for the equality of means T-test. In addition, descriptives were run for subjects’ age and years of

education. Neither age, f(3, 81)=.997, p=.399, nor years of education, f(3,81)=.312, p=.817 was

significantly different across groups.

Overall Word Generation

For total letter score (total words generated during letter verbal fluency tasks), a 2 X 2

multivariate ANOVA testing revealed a main effect for both side, f(1, 81)= 12.718, p= .001, and

lobe, f(1, 81)= 10.445, p= .002. However, no interaction between variables was found, f(1,

81)=.527, p= .470. Further examination using pairwise comparisons showed that damage to the

left side of the brain resulted in greater word generation deficits than damage to the right and

that damage to the frontal lobe resulted in greater word generation deficits than damage to the

temporal lobe.

For total categorization score (total words generated during categorization verbal

fluency tasks), multivariate ANOVA testing revealed a main effect for side, f(1,81)= 24.598,

p= .000, but not for lobe, f(1,81)= .701, p= .405. Once again, no interaction between variables

occurred, f(1,81)= .461, p= .521. Pairwise comparisons revealed that damage to the left side

resulted in greater word generation deficits than damage to the right side.

Furthermore, T-tests were run to look at specific relations between brain regions. For

both letter, p=.119, and categorization tasks, p=.102, differences between the left frontal and

left temporal lobe trended toward, but did not reach significance, where left frontal damage

would be more detrimental to word generation than the left temporal lobe. For letter, p< .001,

and categorization, p< .001, tasks, significance was reached to show that left frontal damage is

significantly more debilitating to word generation than right temporal damage. For letter tasks,

p=.003, significance was found to show that right frontal damage would cause greater damage

to word generation than right temporal damage, but for the categorization task, p=.212,

significance was not found to support this. For the letter, p=.049, and the categorization,

p=.007, tasks, significance was found to support that left frontal damage would be more

harmful to word generation than right frontal damage; similarly, for letter, p=.004, and

45

categorization, p< .001, tasks, significance was found to support that left temporal damage

would create greater word generation deficits than right temporal deficits.

To test to see if low grade tumor subjects significantly affected data, another

multivariate ANOVA was run for subjects only with tumor grades of 3 or 4. Correlating with the

original main effects found, a main effect for side was found for both the categorization task,

f(1, 48)=15.051, p< .001, and letter task, f(1, 48)=6.585, p=.013. A main effect was found again

by lobe for the letter task, f(1, 48)=10.722, p=.002, but not for the categorization task,

f(1,48)=1.184, p=.281. No interaction for the letter task, f(1, 48)=.310, p=.580, or categorization

task, f(1, 48)=.655, p=.422, was found. The same main effects were found before with all tumor

grades included in the analysis; this finding suggests that tumor grade did not significantly

affect data.

Results

Results were found using multivariate analyses of variance and pairwise comparisons.

Significant results were furthered studied using T-tests for equality of means (p < 0.05). When

Levene’s Test for Equality of Variances showed no significance, a minimal degree of error was

presumed and the p value with equal variances assumed was used. When Levene’s Test for

Equality of Variances was significant, the p value with equal variances not assumed was used

for the equality of means T-test. In addition, descriptives were run for subjects’ age and years of

education. Neither age, f(3, 81)=.997, p=.399, nor years of education, f(3,81)=.312, p=.817 was

significantly different across groups.

Overall Word Generation

For total letter score (total words generated during letter verbal fluency tasks), a 2 X 2

multivariate ANOVA testing revealed a main effect for both side, f(1, 81)= 12.718, p= .001, and

lobe, f(1, 81)= 10.445, p= .002. However, no interaction between variables was found, f(1,

81)=.527, p= .470. Further examination using pairwise comparisons showed that damage to the

left side of the brain resulted in greater word generation deficits than damage to the right and

that damage to the frontal lobe resulted in greater word generation deficits than damage to the

temporal lobe.

46

For total categorization score (total words generated during categorization verbal

fluency tasks), multivariate ANOVA testing revealed a main effect for side, f(1,81)= 24.598,

p= .000, but not for lobe, f(1,81)= .701, p= .405. Once again, no interaction between variables

occurred, f(1,81)= .461, p= .521. Pairwise comparisons revealed that damage to the left side

resulted in greater word generation deficits than damage to the right side.

Furthermore, T-tests were run to look at specific relations between brain regions. For

both letter, p=.119, and categorization tasks, p=.102, differences between the left frontal and

left temporal lobe trended toward, but did not reach significance, where left frontal damage

would be more detrimental to word generation than the left temporal lobe. For letter, p< .001,

and categorization, p< .001, tasks, significance was reached to show that left frontal damage is

significantly more debilitating to word generation than right temporal damage. For letter tasks,

p=.003, significance was found to show that right frontal damage would cause greater damage

to word generation than right temporal damage, but for the categorization task, p=.212,

significance was not found to support this. For the letter, p=.049, and the categorization,

p=.007, tasks, significance was found to support that left frontal damage would be more

harmful to word generation than right frontal damage; similarly, for letter, p=.004, and

categorization, p< .001, tasks, significance was found to support that left temporal damage

would create greater word generation deficits than right temporal deficits.

To test to see if low grade tumor subjects significantly affected data, another

multivariate ANOVA was run for subjects only with tumor grades of 3 or 4. Correlating with the

original main effects found, a main effect for side was found for both the categorization task,

f(1, 48)=15.051, p< .001, and letter task, f(1, 48)=6.585, p=.013. A main effect was found again

by lobe for the letter task, f(1, 48)=10.722, p=.002, but not for the categorization task,

f(1,48)=1.184, p=.281. No interaction for the letter task, f(1, 48)=.310, p=.580, or categorization

task, f(1, 48)=.655, p=.422, was found. The same main effects were found before with all tumor

grades included in the analysis; this finding suggests that tumor grade did not significantly

affect data.

47

Figure 5

Clustering and Switching Strategies

Using a 2 X 2 multivariate ANOVA, the total number of semantic clusters produced

during letter tasks revealed a main effect by side, f(1, 81)=4.711, p=.033, by lobe, f(1,

81),=4.372, p=.040, and an interaction, f(1, 81)=5.623, p=.020. Regarding cluster’s average sizes,

data trended toward, but did not reach significance by lobe, f(1, 81)=3.791, p=.055. Further

inspection using pairwise comparisons demonstrated that left side damage had a greater

debilitating effect on generating clusters than right side damage, and that frontal lobe damage

resulted in significantly less clusters and trended towards significantly smaller clusters than

temporal lobe damage. Using T-tests, it was found that left temporal lobe damage caused

significantly fewer clusters to be produced than the right temporal lobe, p=.002, and that right

frontal lobe damage caused significantly fewer clusters to be produced than right temporal

damage, p=.008.

For phonemic scores produced during letter testing, average cluster size, f(1, 81)=6.960,

p=.010, number of clusters produced, f(1, 81)=13.025, p=.001, and number of switches

produced, f(1, 81)=4.211, p=.044, all produced a main effect by side. Using a pairwise

comparison revealed that for all three, damage to the left side resulted in greater strategy

deficits than right side damage. T-tests further demonstrated that for the number of phonemic

clusters produced, left frontal damage would result in greater deficits than right frontal

48

damage, p=.026, and that for the average size of phonemic clusters, the same pattern was

trending, p=.081. T-tests also showed that for phonemic cluster number, p=.008 and trending

for average cluster size, p=.078, left temporal damage would cause greater deficits than right

temporal damage. The same pattern was found trending for the switch number, p=.061.

For semantic scores produced during categorization tasks, average cluster size, f(1,

81)=4.715, p=.033, number of clusters produced, f(1, 81)=13.818, p< .001, and number of

switches produced, f(1, 81)=14.052, p< .001, all produced a main effect by side. Using a

pairwise comparison revealed that for all three, damage to the left side resulted in greater

strategy deficits than right side damage. T-tests demonstrated that left temporal damage

created greater deficits than right temporal damage for both the cluster number, p=.006, and

switch number, p=.004. The T-tests also showed that left frontal damage would result in greater

deficits than right frontal damage for the average cluster size, p=.035, the number of clusters,

p=.016, and the number of switches, p=.035.

For phonemic scores produced during categorization tasks, average cluster size, f(1,

81)=13.897, p< .001, number of clusters produced, f(1, 81)=20.653, p< .001, and number of

switches produced, f(1, 81)=9.722, p=.003, all produced a main effect by side. Using a pairwise


deficits than right side damage. The T-tests further showed that left frontal damage would

result in greater deficits than right frontal damage for the average cluster size, p=.001, and the

number of clusters, p=.004, and trended towards showing that left frontal deficits would cause

greater damage to the ability to produce switches, p=.035. T-tests demonstrated that the left

temporal damage would trend towards causing greater average cluster size deficits, p=.101,

than the right temporal lobe, and the T-test significantly demonstrated that the left temporal

lobe would significantly decrease cluster number, p=.002, and switch number, p=.016, scores in

relation to the right temporal lobe.

49

Figure 6

Figure 7

Figure 5

Clustering and Switching Strategies

50

Using a 2 X 2 multivariate ANOVA, the total number of semantic clusters produced

during letter tasks revealed a main effect by side, f(1, 81)=4.711, p=.033, by lobe, f(1,

81),=4.372, p=.040, and an interaction, f(1, 81)=5.623, p=.020. Regarding cluster’s average sizes,

data trended toward, but did not reach significance by lobe, f(1, 81)=3.791, p=.055. Further

inspection using pairwise comparisons demonstrated that left side damage had a greater

debilitating effect on generating clusters than right side damage, and that frontal lobe damage

resulted in significantly less clusters and trended towards significantly smaller clusters than

temporal lobe damage. Using T-tests, it was found that left temporal lobe damage caused

significantly fewer clusters to be produced than the right temporal lobe, p=.002, and that right

frontal lobe damage caused significantly fewer clusters to be produced than right temporal

damage, p=.008.

For phonemic scores produced during letter testing, average cluster size, f(1, 81)=6.960,

p=.010, number of clusters produced, f(1, 81)=13.025, p=.001, and number of switches

produced, f(1, 81)=4.211, p=.044, all produced a main effect by side. Using a pairwise


deficits than right side damage. T-tests further demonstrated that for the number of phonemic

clusters produced, left frontal damage would result in greater deficits than right frontal

damage, p=.026, and that for the average size of phonemic clusters, the same pattern was

trending, p=.081. T-tests also showed that for phonemic cluster number, p=.008 and trending

for average cluster size, p=.078, left temporal damage would cause greater deficits than right

temporal damage. The same pattern was found trending for the switch number, p=.061.

For semantic scores produced during categorization tasks, average cluster size, f(1,

81)=4.715, p=.033, number of clusters produced, f(1, 81)=13.818, p< .001, and number of

switches produced, f(1, 81)=14.052, p< .001, all produced a main effect by side. Using a

pairwise comparison revealed that for all three, damage to the left side resulted in greater

strategy deficits than right side damage. T-tests demonstrated that left temporal damage

created greater deficits than right temporal damage for both the cluster number, p=.006, and

switch number, p=.004. The T-tests also showed that left frontal damage would result in greater

51

deficits than right frontal damage for the average cluster size, p=.035, the number of clusters,

p=.016, and the number of switches, p=.035.

For phonemic scores produced during categorization tasks, average cluster size, f(1,

81)=13.897, p< .001, number of clusters produced, f(1, 81)=20.653, p< .001, and number of

switches produced, f(1, 81)=9.722, p=.003, all produced a main effect by side. Using a pairwise


deficits than right side damage. The T-tests further showed that left frontal damage would

result in greater deficits than right frontal damage for the average cluster size, p=.001, and the

number of clusters, p=.004, and trended towards showing that left frontal deficits would cause

greater damage to the ability to produce switches, p=.035. T-tests demonstrated that the left

temporal damage would trend towards causing greater average cluster size deficits, p=.101,

than the right temporal lobe, and the T-test significantly demonstrated that the left temporal

lobe would significantly decrease cluster number, p=.002, and switch number, p=.016, scores in

relation to the right temporal lobe.

Figure 6

52

Figure 7

Conclusion

Summary of Main Findings

The results of this study suggest that damage to the left side of the brain in either the

frontal or temporal lobes is most likely to cause deficits to overall word generation abilities in

categorization and letter tasks. Right frontal lobe damage will most likely result in lower overall

word generation deficits during letter, but not semantic, tasks than right temporal lobe

damage. No interaction between brain lobe and side occurred for overall word generation.

Concerning verbal fluency strategies, the number of semantic clusters produced during

letter tasks shows an interaction between side and lobe where left and frontal deficits create a

more significant chance of semantic clustering deficits than right and temporal deficits. This

finding mainly occurred because the right temporal lobe created significantly less fluency

deficits (and scored higher) than any of the other lobes which did not significantly differ from

each other.

For phonemic strategy (clustering, switching) scores during letter and categorization

testing and semantic strategy scores during letter and categorization testing, a main effect by

the left side was discovered, where left side damage resulted in significantly lower scores than

right side damage. T-tests implicated that this significance held for both left versus right

temporal and frontal lobes. In particular, the number of clusters produced was significantly

decreased by left side damage, although the number of switches produced and the average size

of clusters were frequently significant or trending towards significance.

53

Connection to Hypotheses

The first hypothesis was that focal lesions in the left temporal lobe would result in the

comparatively lowest word generation scores for categorization verbal fluency tests. The

second hypothesis was that focal lesions in the left frontal lobe would result in a comparatively

lowest total word generation score in letter verbal fluency tasks. For both categorization and

letter tests’ overall word generation fluency, the left side of the brain did play a significant role,

causing deficits in word generation if a lesion occurred in the frontal or temporal lobes. For

letter tasks, the hypothesis was also correct that frontal lobe damage would be likely to result

in deficits.

The next hypotheses stated that focal lesions in the temporal lobes bilaterally would

result in the lowest clustering scores during categorization and letter fluency tasks, and that

focal lesions in the left frontal lobe would result in a comparatively lowest switching score.

Interestingly, even for the number of semantic clusters produced during letter tasks, the task

was driven by the left and frontal regions of the brain, although the left temporal lobe played a

significant role as well. There was no bilateral component to clustering found; the right

temporal lobe lesions appeared to have the least negative effect on strategy scores. For

strategizing during all other tests, left side damage to the frontal or temporal lobes seemed to

create larger deficits than right side damage. Although this pattern appeared most strongly for

the number of clusters produced, switch number and the average cluster size routinely reached

significance or trended towards it.

Implications

The main results reported above imply that the left side of the brain is critical to word

generation, as well as strategizing during tasks. The left side of the brain is strongly related to

the brain’s language network, and therefore, it would logically follow that tasks involving the

generation and grouping of words would involve the left side of the brain as well.

In addition, the study has implications to support the model for an associative network

critical to language fluency, where the frontal lobe conducts the executive thinking needed for

54

a task and the temporal lobe provides stored information. The frontal lobe plays an especially

important role in letter tasks where there are no preset semantic categories for word

production. Verbal fluency must occur by “novel-generation,” where the quick decision-making

abilities of the frontal lobe are a key component. The frontal lobe also contains Broca’s area,

which is necessary for forming words. Since the temporal lobe did not have a main effect for

categorization tasks, and was not “more important” to the task than the frontal lobe, it can be

assumed that both the left frontal and temporal lobes remain equally important for

categorization tasks. That is, while the executive frontal lobe still remains useful to word

generation, the temporal lobe is able to become useful in retrieving stored words. The top-

down processing capabilities of the temporal lobe can specify which words belong to a certain

semantic category, allowing for more effective word retrieval, and the temporal lobe’s

Wernicke’s area is critical to understanding words. On the other hand, right temporal lobe

damage was not seen to cause significant deficits in verbal fluency abilities. This may be

because the medial and right temporal lobe stores more personal and automated information

compared to the general information retrieved from the left temporal lobes during verbal

fluency tasks.

Regarding strategies, one of the most interesting findings was the significant interaction

by side and lobe for the number of semantic clusters produced during letter tasks. The

interaction was mainly found because right temporal lobe damage impacted the cluster

number score must less than damage to any of the other lobes. The results again pointed

towards an associative network, even during letter tasks, (where, for total word generation,

significance was found for the frontal lobe’s primary role). An associative network would

assume that the frontal lobe was being activated for general executive functioning, finding and

“choosing” words for the task, and for its role in novel generation during letter tasks.

Meanwhile, the significance found for left temporal lobe damage to result in lower scores

probably was related to the number of clusters produced; the left temporal lobe is frequently

considered important for the grouping of information (clusters) because it contains the

information to be grouped. This view of the left temporal lobe is especially applicable to

semantic clustering, where the information is being organized according to the top-down

55

processing the left temporal lobe utilizes. Also intriguing is the role the right frontal role played

in semantic clustering during letter tasks. Its role could perhaps be to assist the left frontal lobe

with executive thinking or novel generation, and it can be considered a possible part of the

associative verbal fluency network that is subject to more research.

For phonemic strategy scores during letter and categorization testing and semantic

strategy scores during letter and categorization testing, the findings that damage to the left

hemisphere of the brain would result in significantly lower scores than damage to the right

hemisphere contributed to the evidence of a corresponding frontal-temporal network. The

finding again implied that the (left) temporal and frontal lobes are both necessary for verbal

fluency, again with the implication for strategies that the temporal lobe was used more for

semantics or driving clustering while the frontal lobe specialized in executive thinking,

phonemics, and creating switches between groups. However, it was important to see in results

than even for semantic clustering or phonemic switching, neither damage to the left frontal nor

left temporal lobe would result in significantly worse scores—both lobes, in whatever case,

both played a necessary role.

The results for this study also have applications regarding the guidelines used for

scoring. Previous scoring guidelines for clustering and switching have been unspecific. This

study strived to create clear guidelines for scoring based on both previous study

recommendations and on precise, logical methods of categorization. For instance, by clearly

defining how zoological categories should be defined, an explainable methodology for

clustering animals was made. The fact that the general findings of this study were significant

and correlated with other studies shows that these guidelines are useable and may open up for

a more reliable way of quantifying clusters and switches. The study also made guidelines for

how to cluster semantically on letter tasks and cluster phonemically on categorization tasks,

two areas that have been rarely researched and lacked clear scoring guidelines previously.

Future Recommendations

The results regarding strategies very strongly implied that a left side network is

necessary for producing a large quantity of clusters, but the results were less consistently

significant regarding the average size of clusters and number of switches. Future studies can do

56

more work to analyze these strategy scores to see if the significant results regarding these

strategies occurred by chance or not in the current study. Doing so can help to compare and

contrast what parts of the brain are important to the specific strategies, individualizing the

strategies to see their similar and dissimilar qualities.

Future studies should also consider the role of repetitions in disrupting verbal fluency

strategies. When a repetition occurred between two words, those words were not counted in

the same cluster since the repetition was disturbing the novel generation of words within the

given tasks. A future study might go back and analyze the role of repetitions in causing strategy

and clustering deficits. That is, if repetitions are a significant cause of decreasing the number of

clusters, they might be the reason for deficits seen. Analyzing repetitions and what brain

damage makes them more likely to be created as a next step would be particularly useful

clinically since repetitions are a clear sign of deficits and do not take excessive time for the

examiner to score on a verbal fluency test. In other words, if future studies found repetitions to

also be associated with certain brain regions, repetitions could be used as a preliminary

measure of where patients’ brain damage occurs.

Within the study, one way to improve results in the future would be to add to the n of

the left temporal subjects in the study, which may have been underpowered and decreased the

ability to see interactions that were trending towards significance. An example of this can be

seen concerning the overall word generation scores, especially for letter fluency. In addition,

raising the overall number of subjects in the study could be useful as well when finding

significance in T-tests. For instance, some results gathered from the T-tests should be regarded

with caution, as the degree of error was relatively large between groups (as shown by Levene’s

Test of the Equality of Means); however, a problem like this would most likely decrease with

more subjects. In addition, many T-tests were run—the mere quantity again means that data

should be interpreted with caution, but with more subjects, significant results found would be

more reliable.

In addition, the current study began looking at only higher tumor grades for overall

word generation and found the same main effects as were found with all tumor grades,

suggesting that tumor grade did not make a significant difference in results. At the same time, a

57

future study should consider comparing all high tumor grade patients against lower grade

patients to see the real difference in damage that high grade, more destructive tumors may

cause to verbal fluency than low grade, less harmful tumors. Using high grade tumor subjects in

general would also contribute to more reliable results, as all subjects’ tumors would be very

debilitating to their verbal fluencies abilities. Knowing that subjects’ functioning was being

harmed greatly would help increase confidence that the results of the lesion study truly

represented areas of the brain most important to verbal fluency tasks.

The last future recommendation would be adding a control group to the current project

to compare lesion groups. Adding a control group would further allow for the relationships

between brain regions presented in this study to be analyzed. For instance, a control group

could show if right temporal lesions have any effect on verbal fluency, as they comparatively

appeared to have the least effect within the current study. Also, having a control group would

give a good measure of how much damage, for example, a left frontal lesion can cause to verbal

fluency scores in comparison to the average verbal fluency abilities in healthy subjects.

Although the current study was important for researching the relative importance of brain

regions for verbal fluency and verbal fluency strategies, adding a control group is a logical next

step.

58

Bibliography

Alexander, Michael P. et al. “Lateralized Cerebellar Contributions to Word Generation: A

Phonemic and Semantic Fluency Study.” Behavioural Neurology, 2012; 23(1-2): 31-37.

IDS Press. Web. 30 Jul. 2012.

Ali, Nilufa et al. “Structural Correlates of Semantic and Phonemic Fluency Ability in First and

Second Languages.” Cereb. Cortex, Nov. 2009; 19(11): 2690-2698. NCBI. Web. 30 Jul.

2012.

Amunts K. “Within-task Switching in the Verbal Domain.” Neuroimage, Nov. 2003; 20. PubMed.

Web. 31 Jul. 2012.

Aylward, Elizabeth et al. “Category-specific naming and recognition deficits in temporal lobe

epilepsy surgical patients.” Neuropsychologia, 2008: 46(5):1242-1255. Elsevier and

SciVerse. Web. 22 Aug. 2012.

Baciu, Monica et al. “Hemispheric Predominance Assessment of Phonology and Semantics: A

Divided Visual Field Experiment.” Brain and Cognition, 2006; 61: 298-304. Elsevier. Web.

30 Jul. 2012.

Badewien, Meike. “Differential Prefrontal and Frontotemporal Oxygenation Patterns During

Phonemic and Semantic Verbal Fluency.” Neuropsychologia, June 2012; 50(7): 1565-

1569. Elsevier and ScienceDirect. Web. 31 Jul. 2012.

Baldo, Juliana et al. “Pervasive Influence of Semantics in Letter and Category Fleuncy: A

Multidimensional Approach.” Brain and Language, 2003, Academic Press. Web. 31 Jul.

2012.

59

Baldo, Juliana et al. “Role of Frontal Versus Temporal Corte in Verbal Fluency as revealed by

Voxel-Based Lesion Symptom Mapping.” J. Int. Neuropsychol. Soc., Nov. 2006; 12(6):

896-900. PubMed. Web. 30 Jul. 2012.

Barker, R.A. et al. “Verbal Fluency in Huntington’s Disease: A Longitudinal Analysis of Phonemic

and Semantic Clustering and Switching.” Neuropsychologia, 2002; 40(8): 1277-84.

Elsevier. Web. 31 Jul. 2012.

Barton, Emily A. “Levels of Processing: The Effects of Orthographic, Phonologic, and Semantic

Processing on Memory.” Student Pulse, 2012. Web. 30 Jul. 2012.

Baudu, C. et al. “Clustering and Switching Strategies in Verbal Fluency Tasks: Comparison

Between Schizophrenics and Healthy Adults.” J. Int. Neuropsycho. Soc., 1998; 4(6): 539-

46. PubMed. Web. 31 Jul. 2012.

Beaucousin, V. et al. “Meta-analyzing Left Hemisphere Language Area: Phonology, Semantics,

and Sentence Processing.” Neuroimage, May 2006; 30(4): 1414-32. PubMed. Web. 30

Jul. 2012.

Bilar, WB et al. “Sex Differences in Clustering and Switching in Verbal Fluency Tasks.” J. Int.

Neuropsychol. Soc., Jul 2006; 12(4): 502-9. PubMed. Web. 31 Jul. 2012.

Blumenfeld, Hal. Neuroanatomy Through Clinical Cases. Sunderland: Sinauer Associates Inc.,

2002. Print.

“Brain Structures and Their Functions.” Serendip, 1994. Bryn Maur College. Web. 25 Jul. 2012.

Campbell and Reece. AP Edition Biology. San Francisco: Pearson Education, Inc., 2005. Print.

60

“Cancer Prevalence: How Many People Have Cancer?” American Cancer Society, 2012. Web. 24

Aug. 2012.

Carlson, Synnove et al. “Attention and Semantic Processing During Speech: An fMRI Study.”

Brain and Cognition Aug. 2012; 122(12): 114-119. ScienceDirect. Web. 30 Jul. 2012.

Castillo, Joseph. “Fundamentals of Image Interpretation.” Web. 21 Jul. 2012.

“CSF.” Dictionary.com, 2012. Web. 12 Jul. 2012.

Damasio, Antonio and Meyer, Kaspar. “Convergence and Divergence in a Neural Architecture for Recognition and Memory.” Trends in Neuroscience, July 2009; 32(7): 376-382. SciVerse. Web. 22 Aug. 2012.

Das, Rajesh et al. Orthographic Viewer. Eplasty. Objective Three-Dimensional Analysis of Cranial Morphology. Edited Image. 13 Aug. 2012.

DeAngelis, Lisa M. Intracranial Tumors. Martin Dunitz Ltd, 2002. Print.

Dennett, Daniel C. “Review of Demasio, Descartes’ Error.” Times Literary Supplement, Aug. 1995: 3-4. Tufts University. Web. 22 Aug. 2012.

Diesendruck, Gil. “Categories for Names or Names for Categories? The Interplay Between Domain-Specific Conceptual Structure and Language.” Language and Cognitive Processes, 2003; 18(5/6): 759-787. Bar-Ilan University. Web. 28 Aug. 2012.

Duffau, Hugues and Martiz-Gasser, Sylvie. “Evidence of a Large-Scale Network Underlying

Language Switching: A Brain Stimulation Study.” J. Neurosurg, 2009; 111: 729-732. Joint

Media News Service. Web. 30 Jul. 2012.

Flaherty, Alice W. and Rost, Natalia S. The Massachusetts General Hospital Handbook of

Neurology. Philadelphia: Lippencott Williams & Wilkins, 2007. Print.

“Furniture Categories.” McKay’s Furniture. Web. 28 Aug. 2012.

61

Grabowska, Anna et al. “Phonological and Semantic Fluencies are Mediated by Different

Regions of the Prefrontal Cortex.” Acta. Neurobiol. Exp., 2000; 60: 503-508. Web. 30 Jul.

2012.

“Gray Matter vs. White Matter.” Neuroscience Intelligence: Behavioral Neuroscience Web Ring

[at] Macalester College. Web. 14 Jul 2012.

Horemans, I. et al. “The Influence of Semantic and Phonological Factors on Syntactic Decisions:

An Event-Related Brain Potential Study.” Psychophysiology, Nov 2003; 40(6): 869-77.

PubMed. Web. 30 Jul. 2012.

John, Sunila et al. “Qualitative Analysis of Clustering on Verbal Fluency in Young Adults.”

Language in India, Jul. 2011; 11. Web. 31 Jul. 2012.

Leggio, Maria Giuseppa et al. “Phonological Grouping is Specifically Affected in Cerebellar

Patients: A Verbal Fluency Study.” J. Neurol. Neurosurg. Psychiatry, 2000; 69:102-106.

BMS Publishing Group. Web. 31 Jul. 2012.

“Lesion.” Dictionary.com, 2012. Web. 12 Jul. 2012.

“Lexical.” Dictionary.com, 2012. Web. 29 Jul. 2012.

MacAndrew, Alec. “FOXP2 and the Evolution of Language.” Alec’s Evolution Pages, 2003. Web.

2 Sept. 2012.

Moscovitch, Morris and Sheldon, Signy. “The Nature and Time-Course of Medial Temporal Lobe

Contributions to Semantic Retrieval: An fMRI Study on Verbal Fluency.” Hippocampus,

June 2012; 22(6): 1451-1466. Wiley Periodicals. Web. 31 Jul. 2012.

62

MRI of the Brain following gadolinium demonstrating enhancement of MS lesions. 2012.

University of Maryland Medical Center. The Maryland Center for Multiple Sclerosis.

Image. 13 Aug. 2012.

“Nervous Tissue.” Rutgers University. 2012. Web. 12 Jul. 2012.

Overney, Gregor T. “Exploration of Human Brain Tissue.” Microscopy UK, 2002. Web. 12 Jul.

2012.

“Paraphasia.” Dictionary.com, 2012. Web. 29 Jul. 2012.

“Pars Orbitalis.” Dictionary.com, 2012. Web. 29 Jul. 2012.

“Phoneme.” Dictionary.com, 2012. Web. 29 Jul. 2012.

“Posterior.” The Free Dictionary, 2012. Farlax. Web. 8 Aug. 2012.

“Prelexical.” Dictionary.com, 2012. Web. 29 Jul. 2012.

Price, Cathy J. “The Anatomy of Language: A Review of 100 fMRI Studies Published in 2009.”

Annals of the New York Academy of Sciences, 2912; 1191: 62-88. Print.

“Semantics.” Dictionary.com, 2012. Web. 29 Jul. 2012.

Sherman, Elisabeth MS et al. A Compendium of Neuropsychological Tests. New York: Oxford

University Press, 2006. Print.

Snell, Richard S. Clinical Neuroanatomy for Medical Students. Philadelphia: Lippincott-Raven

Publishers, 1997. Print.

63

“Syntax.” Dictionary.com, 2012. Web. 29 Jul. 2012.

“Top-down Processing.” Dictionary.com, 2012. Web. 29 Jul. 2012.

Tranel, Daniel. “Impaired Naming of Unique Landmarks is Associated with Left Temporal Polar

Damage.” Neuropsychology, 2006; 20(1): 1-10. American Psychological Association.

Print.

Troyer, Angela K. “Clustering and Switching as Two Components of Verbal Fluency: Evidence

from Younger and Older Healthy Adults.” Neuropsychology, 1997; 11: 138-146. Baycrest.

Web. 31 Jul. 2012.

Troyer, Angela K. “Clustering and Switching on Verbal Fluency: The Effects of Focal Frontal and

Temporal Lobe Lesions.” Neuropsychologia, June 1998; 36(1): 499-504. Elsevier and

ScienceDirect. Web. 31 Jul. 2012.

Troyer, A.K. “Normative Data for Clustering and Switching on Verbal Fluency Tasks.” Journal of

Clinical and Experimental Neuropsychology, 2010; 22(3): 370-378. Web. 14 Jan 2013.

Untitled. 1995. Intelegen Inc. Overview of the Brain. Image. 13 Aug. 2012.

64

Documents

Paper.docx · Web viewdetermining the origin of clustering and switching abilities during verbal fluency tasks: a lesion study. abstract